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Description  |
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BACKGROUND OF THE INVENTION
This invention relates to novel derivatives of
9-deoxo-9a-aza-9a-homoerythromycin A and of its 4"-epimer useful as
antibacterial agents, to intermediates therefor, and to processes for
preparation of said derivatives and said intermediates. More particularly
it relates to cyclic ether derivatives of
9-deoxo-9a-aza-9a-homoerythromycin A and of its 4"-epimer, to
pharmaceutically acceptable acid addition salts thereof and the use of
said compounds as antibacterial agents, to intermediates therefor, and to
processes for their preparation.
Erythromycin A is a macrolide antibiotic produced by fermentation and
described in U.S. Pat. No. 2,653,899. Numerous derivatives of erythromycin
A have been prepared in efforts to modify its biological and/or
pharmacodynamic properties. Erythromycin A esters with mono- and
dicarboxylic acids are reported in Antibiotics Annual, 1953-1954, Proc.
Symposium Antibiotics (Washington, D.C.), pages 500-513 and 514-521,
respectively. U.S. Pat. No. 3,417,077 describes the cyclic carbonate ester
of erythromycin A, the reaction product of erythromycin A and ethylene
carbonate, as an active antibacterial agent.
U.S. Pat. No. 4,328,334, issued May 4, 1982 describes
9-deoxo-9a-aza-9a-homoerythromycin A and refers to it by the name
11-aza-10-deoxo-10-dihydroerythromycin A. Since said compound is a ring
expanded (homo) derivative of erythromycin A, nitrogen (aza) being the
additional atom of the ring system, the nomenclature
9-deoxo-9a-aza-9a-homoerythromycin A is preferred for the parent ring
system of the compounds of this invention.
Belgian Patent No. 892,357, published July 1, 1982, and its British
counterpart, Application No. 2,094,293A, published Sept. 15, 1982,
disclose the N-methyl derivative of 9-deoxo-9a-aza-9a-homoerythromycin A,
as does my copending U.S. application Ser. No. 441,981, filed Nov. 15,
1982, which claims priority from U.S. application Ser. No. 399,401, filed
July 19, 1982. The 4"-epimer of said N-methyl derivative is the subject of
my copending U.S. application Ser. No. 441,979, filed Nov. 15, 1982. U.S.
Pat. No. 4,382,085, issued May 3, 1983 describes 4"-epi erythromycin A;
i.e., the 4"--OH group has the axial configuration. The 4"--OH in
erythromycin A has the equatorial configuration.
SUMMARY OF THE INVENTION
It has now been found that certain cyclic ethers of
9-deoxo-9a-aza-9a-homoerythromycin A and of its 4"-epimer are effective
antibacterial agents against Gram-positive and Gram-negative bacteria. The
compounds have the formula (I)
##STR1##
wherein n is 1, 2 or 3; and the wavy line at the 4"-position is generic to
and embracive of both epimer forms, provided that when n is 1, the
4"-hydroxy group possesses the equatorial configuration. When n is 2 or 3,
the epimeric forms of said compound differ structurally only in the
configuration of the chiral center at the 4"-position; i.e., the 4"--OH
group is either axial or equatorial. The axial configuration is
represented by a solid or wedged shape line and the equatorial by a broken
line of attachment of the OH group to the 4"-position. The terms "axial"
and "equatorial" as used herein refer to the two possible chiral epimers
at C--4" with respect to the 4"-hydroxyl and hydrogen.
Also included in this invention, and useful for the same purpose as formula
(I) compounds, are the pharmaceutically acceptable acid addition salts
thereof. Included among said slats, but by no means limited to said salts,
are those enumerated below: hydrochloride, hydrobromide, sulfate,
phosphate, formate, acetate, propionate, butyrate, citrate, glycolate,
lactate, tartrate, malate, maleate, fumarate, gluconate, stearate,
mandelate, pamoate, benzoate, succinate, lactate, p-toluenesulfonate and
aspartate.
The present invention also embraces processes and intermediates useful for
the preparation of compounds of formula (I). The intermediates are
represented by formulae (II) and (III) below:
##STR2##
wherein R.sub.1 is --(CH.sub.2).sub.p CN or --(CH.sub.2).sub.m --NH.sub.2
; p is 1 or 2 and m is 2 or 3; and
##STR3##
wherein the wavy line at the 4"-position of each of formulae II and III
represents both epimers; i.e., the axial and equatorial configurations, at
said position.
Also included in this invention are the compounds of formula (IV) which are
formed as by-products in preparation of formula (I) compounds wherein n is
3:
##STR4##
wherein the wavy line at the 4"--OH group represents the axial and
equatorial configurations at said position.
Compounds of formulae (I), (II) and (IV) and pharmaceutically acceptable
acid addition salts thereof are effective antibacterial agents against
Gram-positive microorganisms, e.g. Staphylococcus aureus and Streptococcus
pyrogenes, and against Gram-negative microorganisms, e.g. Pasturella
multocida and Neisseria sicca in vitro. Additionally, compounds of formula
(I) exhibit significant activity against Neisseria gonorrhea and
Haemophilus in vitro and against many Gram-positive and Gram-negative
microorganisms in vivo. In their oral anti-infective activity the formula
(I) compounds are like 9-deoxo-9a-methyl-9a-aza-9a-homoerythromycin A, and
quite unlike the corresponding 9a-desmethyl compound
9-deoxo-9a-aza-9a-homoerythromycin A which exhibits no practical oral
activity in vivo.
DETAILED DESCRIPTION OF THE INVENTION
The compounds of formula (I) wherein n is 3 are prepared by cyanoethylation
of the appropriate 9-deoxo-9a-aza-9a-homoerythromycin A epimers. An excess
of acrylonitrile serves as both reactant and solvent. The reaction is
generally carried out at the reflux temperature of the acrylonitrile
solvent, about 77.degree. C. until reaction is complete. Lower
temperatures, e.g. 50.degree. C. can be used but are avoided because of
the longer reaction periods required. Higher temperatures can be used by
using a solvent other than excess acrylonitrile and which is
reaction-inert; i.e., does not enter into reaction with reactants and/or
products so as to adversely affect the yield of the desired cyanoethyl
derivative. A reaction-inert solvent can, of course, be used at whatever
temperature the reaction is run. Suitable solvents are C.sub.1-4 alcohols,
ether (cyclic and acylic) such as dioxan, tetrahydrofuran, diethyl ether,
diethylene glycol, dimethyl ether, aromatic hydrocarbons such as benzene,
toluene and xylene. However, the preferred method comprises the use of
excess acrylonitrile as solvent.
The progress of the reaction is monitored by thin layer chromatography
(TLC) on silica gel plates and elution thereof with CH.sub.2 Cl.sub.2
/CH.sub.3 OH/concentrated NH.sub.4 OH (6/1/0.1) and development of the
plates with a spray of vanillin/ethanol/H.sub.3 PO.sub.4 and heat.
The product is recovered by evaporation of the solvent as an off-white
foam. It can be, and for convenience is, used directly in the next step of
the process as is. TLC indicates the product is principally the desired
monocyanoethylated product. Trace amounts of more polar products were
detected on TLC.
The 9a-cyanoethyl derivative (II) thus produced is converted to the
corresponding 9a-(gamma-aminopropyl) derivative (II) by means of
hydrogenation over Raney nickel according to the procedure described
herein. It is converted to the corresponding 7-membered ring cyclic ether
by reaction of at least stoichiometric amounts of each of isoamyl nitrite
and glacial acetic acid according to the procedure described herein. The
compound of formula (IV), the corresponding 9a-(gamma-acetoxypropyl)
derivative is produced as by-product.
The formula I compounds wherein n is 2 are prepared by alkylation of the
appropriate 4"--OH epimer of 9-deoxo-9-aza-9a-hydroxy-9a-homoerythromycin
A 3'--N-oxide in a reaction-inert solvent with preferably an excess of
bromoacetonitrile at from 20.degree. C. to 100.degree. C. and preferably
at room temperature. Suitable solvents are chlorinated hydrocarbons such
as methylene chloride, chloroform, aromatic hydrocarbons such as benzene,
toluene, xylene, ethers such as diethylene glycol dimethyl ether, dioxan,
tetrahydrofuran, diethyl ether.
The reaction is carried out in the presence of an acid acceptor, e.g. an
organic base such as a C.sub.1-4 trialkylamine, pyridine or an inorganic
base such as an alkali metal carbonate or bicarbonate. The acid acceptor
is used in equimolar proportion to the bromoacetonitrile which is
generally used in excess to ensure optimum conversion of the macrolide
reactant to product.
Catalytic hydrogenation of (III) over Pd/C in a reaction-inert solvent such
as ethanol achieves removal of the 9a- and 3'-oxide groups to yield the
cyanomethyl compound of formula (II) wherein p is 1.
The 9a-cyanomethyl derivative [formula (II)] thus produced is reduced to
the corresponding 9a-(beta-aminoethyl) derivative (II) by means of sodium
borohydride in the presence of cobaltous chloride in hydroxylic or
non-hydroxylic solvents at room temperature. Molar ratios of CoCl.sub.2 to
NaBH.sub.4 of about 1:5 are favored for this reduction. In practice an
excess of NaBH.sub.4 is used; e.g. up to 10 moles of NaBH.sub.4 per mole
of substrate. Reaction of the 9a-(beta-aminoethyl) derivative with at
least stoichiometric amounts of each of isoamylnitrite/glacial acetic acid
affords the corresponding 6-membered ring cyclic ether.
The 5-membered ring cyclic ether of formula I (n=1, 4"--OH=equatorial
configuration) is prepared by reacting 9-deoxo-9a-aza-9a-homoerythromycin
A with from 1-4 equivalents each of formaldehyde, conveniently as 37%
aqueous solution, and formic acid, in a reaction-inert solvent, preferably
at ambient temperature. Representative solvents are halogenated
hydrocarbons such as methylene chloride, chloroform and carbon
tetrachloride.
The critical feature of the reaction is the use of relatively low reaction
temperature. The reaction is readily conducted from about 15.degree. C. to
30.degree. C., preferably from 20.degree. C.-25.degree. C. The reaction,
if conducted at elevated temperatures, e.g. reflux temperature, affords
the 9a-methyl derivative; i.e., reductive methylation occurs. At elevated
temperatures, e.g. above about 50.degree. C., methylation occurs
exclusively. However, under the conditions of the present process cyclic
ether formation occurs between the 11beta-OH and the 9a-aza groups.
Compounds of formulae (I), (III) and (IV) and of formula (II) wherein
R.sub.1 is --(CH.sub.2).sub.p CN wherein the 2' and/or 4"-hydroxy groups
are acylated to give corresponding C.sub.2-3 alkanoyl derivatives are
conveniently prepared by standard acylation procedures such as those
described by Jones et al., J. Med. Chem. 15, 631 (1972), and by Banaszek
et al., Rocy. Chem. 43, 763 (1969). The 2'- and 4"-hydroxy groups are
acylated by means of the appropriate acid anhydride [e.g. (R.sub.2
CO).sub.2 O] in pyridine. Solvolysis of the 2',4"-ester with methanol
produces the 4"-ester.
Formation of mixed esters, e.g. 2'-acetyl-4"-propionyl-, is readily
achieved by acylating the 4"-ester (R.sub.3 =propionyl) with acetic
anhydride in a reaction-inert solvent in the presence of potassium
carbonate according to the procedure for mixed esters described by Jones
et al. (loc, cit.).
Acid addition salts of the compounds of this invention are readily prepared
by treating compounds having formulae I-IV with at least an equimolar
amount of the appropriate acid in a reaction-inert solvent or, in the case
of the hydrochloride salts, with pyridinium hydrochloride. Since more than
one basic group is present in a compound of formula I or II, the addition
of sufficient acid to satisfy each basic group permits formation of
polyacid addition salts. When preparing acid addition salts of formulae
I-IV compounds wherein the 2'--OH is acylated, isopropanol is used as
solvent to avoid solvolysis of the alkanoyl group. The acid addition salts
are recovered by filtration if they are insoluble in the reaction-inert
solvent, by precipitation by addition of a non-solvent for the acid
addition salt, or by evaporation of the solvent.
A variety of gram-positive microorganisms and certain gram-negative
microorganisms, such as those of spherical or ellipsoidal shape (cocci),
are susceptible to compounds of formulae (I), (II) and (IV). Their in
vitro activity is readily demonstrated by in vitro tests against various
microorganisms in a brain-heart infusion medium by the usual two-fold
serial dilution technique. Their in vitro activity renders them useful for
topical application in the form of ointments, creams and the like, for
sterilization purposes, e.g. sick-room utensils; and as industrial
antimicrobials, for example, in water treatment, slime control, paint and
wood preservation.
For in vitro use, e.g. for topical application, it will often be convenient
to compound the selected product by methods well known in the pharmacist's
art into lotions, salves, ointments, creams, gels or the like. For such
purposes, it will generally be acceptable to employ concentrations of
active ingredient of from about 0.01 percent up to about 10 percent by
weight based on total composition. The dosage form is applied at the site
of infection ad libitum, generally at least once a day.
Additionally, formula (I) compounds of this invention are active versus
Gram-positive and certain Gram-negative microorganisms in vivo via the
oral and/or parenteral routes of administration in animals, including man.
Their in vivo activity is more limited as regards susceptible organisms
and is determined by the usual procedure which comprises infecting mice of
substantially uniform weight with the test organism and subsequently
treating them orally or subcutaneously with the test compound. In
practice, the mice, e.g. 10, are given an intraperitoneal inoculation of
suitably diluted cultures containing approximately 1 to 10 times the
LD.sub.100 (the lowest concentration of organisms required to produce 100%
deaths). Control tests are simultaneously run in which mice receive
inoculum of lower dilutions as a check on possible variation in virulence
of the test organism. The test compound is administered 0.5 hour
post-inoculation, and is repeated 4, 24 and 48 hours later. Surviving mice
are held for 4 days after the last treatment and the number of survivors
is noted.
When used in vivo, these novel compounds can be administered orally or
parenterally, e.g. by subcutaneous or intramuscular injection, at a dosage
of from about 1 mg/kg to about 200 mg/kg of body weight per day. The
favored dosage range is from about 5 mg/kg to about 100 mg/kg of body
weight per day and the preferred range from about 5 mg/kg to about 50
mg/kg of body weight per day. Vehicles suitable for parenteral injection
may be either aqueous such as water, isotonic saline, isotonic dextrose,
Ringer's solution or non-aqueous such as fatty oils of vegetable origin
(cotton seed, peanut oil, corn, sesame), dimethylsulfoxide and other
non-aqueous vehicles which will not interfere with therapeutic efficiency
of the preparation and are non-toxic in the volume or proportion used
(glycerol, propylene glycol, sorbitol). Additionally, compositions
suitable for extemporaneous preparation of solutions prior to
administration may advantageously be made. Such compositions may include
liquid diluents; for example, propylene glycol, diethyl carbonate,
glycerol, sorbitol, etc.; buffering agents, hyaluronidase, local
anesthetics and inorganic salts to afford desirable pharmacological
properties. These compounds may also be combined with various
pharmaceutically-acceptable inert carriers including solid diluents,
aqueous vehicles, non-toxic organic solvents in the form of capsules,
tablets, lozenges, troches, dry mixes, suspensions, solutions, elixirs and
parenteral solutions or suspensions. In general, the compounds are used in
various dosage forms at concentration levels ranging from about 0.5
percent to about 90 percent by weight of the total composition.
In the examples presented herein, no effort was made to recover the maximum
amount of product produced or to optimize the yield of a given product.
The Examples are merely illustrative of the process and of the products
obtainable thereby.
In all examples, the terms "vanillin/ethanol/H.sub.3 PO.sub.4 spray" and
"vanillin/H.sub.3 PO.sub.4 spray" refer to a solution of 1.0 g of
vanillin, 100 ml of ethanol and 100 ml of H.sub.3 PO.sub.4.
EXAMPLE 1
4"-Epi-9-deoxo-9a-(beta-cyanoethyl)-9a-aza-9a-homoerythromycin A
4"-Epi-9-deoxo-9a-aza-9a-homoerythromycin A (11.6 g, 15.8 mmole) was
dissolved in 100 ml of acrylonitrile. The solution was refluxed for 19
hours, and then concentrated in vacuo, affording an ivory foam. Tlc
inspection (silica gel plates; elution with CH.sub.2 Cl.sub.2 /CH.sub.3
OH/concentrated NH.sub.4 OH=6/1/0.1; vanillin/H.sub.3 PO.sub.4 spray with
heat; R.sub.f =0.51) revealed a single (less polar) dominant product with
only trace amounts of (more polar) impurities. The crude product was used
in the next step without further purification.
.sup.13 C-nmr [CDCl.sub.3, (CH.sub.3).sub.4 Si internal standard] ppm
177.92 (lactone>C.dbd.O), 118.86 (--C.tbd.N), 102.49 (C--1'), 96.04
(C--1"), 40.25 [(CH.sub.3).sub.2 N--].
EXAMPLE 2
4"-Epi-9-deoxo-9a-(gamma-aminopropyl)-9a-aza-9a-homoerythromycin A
A solution of 12.8 g (16.2 mmoles) of
4"-epi-9-deoxo-9a-(beta-cyanoethyl)-9a-aza-9a-homoerythromycin A in 250 ml
of absolute ethanol was combined with 12.8 g of Raney-Ni catalyst (50%
water-wet) and hydrogenated on a Parr apparatus at 50 psi (3.52
kg/cm.sup.2) for 19 hours. Tlc monitoring (silica gel plates; elution with
CHCl.sub.3 /CH.sub.3 OH/concentrated NH.sub.4 OH=6/1/0.1; vanillin/H.sub.3
PO.sub.4 spray with heat; R.sub.f =0.13) showed complete reaction. The
catalyst was filtered and the filtrate concentrated in vacuo to a foam.
The crude product was dissolved in ca. 100 ml of methylene chloride. The
solution was shaken with an equal volume of saturated aqueous sodium
bicarbonate, the organic phase separated, dried with sodium sulfate, and
concentrated in vacuo to an ivory foam (10.5 g). The entire sample was
crystallized from warm ether, yielding 4.0 g, mp 135.degree. C. (dec.).
.sup.13 C-nmr [(CDCl.sub.3, (CH.sub.3).sub.4 internal standard] ppm 177.07
(lactone>C.dbd.O), 102.22 (C--1'), 95.77 (C--1"), 40.30 [(CH.sub.3).sub.2
N--].
EXAMPLE 3
4"-Epi-9,11-deoxo-11beta,9a-(epoxypropano)-9a-aza-9a-homoerythromycin A
[Formula (I), n=3,4"-axial hydroxy] and
4"-Epi-9-deoxo-9-a-(gamma-acetoxypropyl)-9a-aza-9a-homoerythromycin A
To a solution of
4"-epi-9-deoxo-9a-(gamma-aminopropyl)-9a-aza-9a-homoerythromycin A (3.37
g, 4.3 mmole) in 20 ml of chloroform, 574 mg (0.66 ml; 4.9 mmole) of
isoamyl nitrite and 511 mg (8.52 mmole) of glacial acetic acid were added,
and the mixture was vigorously refluxed for one hour. Tlc examination
showed complete reaction and the presence of two major components (silica
gel tlc plates momentarily immersed in a formamide/acetone solution and
then air-dried; elution with CHCl.sub.3 /acetone=1/1; vanillin/H.sub.3
PO.sub.4 spray with heat). The reaction mixture was shaken with 50 ml of
10% aqueous potassium carbonate. The organic phase was then separated,
washed with 50 ml of saturated brine solution, dried over sodium sulfate,
and concentrated in vacuo to a colorless foam (3.17 g).
Formamide-treated silica gel was prepared by adding 120 ml of formamide to
a well-stirred 300 g silica gel (230-240 mesh)/600 ml acetone slurry; and
then rotoevaporating solvent until a free-flowing powder was obtained. The
crude product was chromatographed on 300 g of formamide-impregnated silica
gel, eluting with CHCl.sub.3 /hexane=98/2 and monitoring collected
fractions by tlc (utilizing the abovedescribed tlc system). Thus the two
components produced in the reaction--the (less polar) title compound (344
mg, 10% yield), and
4"-epi-9-deoxo-9a-(gamma-acetoxypropyl)-9a-aza-9a-homoerythromycin A (400
mg; 11% yield)--were isolated as colorless amorphous solids.
In a second analogous run the chromatographed title compound (162 mg) was
crystallized from acetone/water (yielding 94 mg, m.p.
139.degree.-141.degree. C.).
4"-Epi-9,11-deoxo-11beta,9a-(epoxypropano)-9a-aza-9a-homoerythromycin A:
.sup.1 H-nmr (CDCl.sub.3) delta 2.28 [6H, s, (CH.sub.3).sub.2 N--], 3.28
(3H, s, cladinose CH.sub.3 O--); .sup.13 C-nmr [CDCl.sub.3,
(CH.sub.3).sub.4 Si internal standard] ppm 176.28 (lactone>C.dbd.O),
102.36 (C--1'), 96.18 (C--1"), 40.26 [(CH.sub.3).sub.2 --N--]; mass
spectrum (m/e) 774 (molecular ion), 616.4, 599.4, 458,3, 442.3, 158.2,
127.1.
4"-Epi-9-deoxo-9a-(gamma-acetoxypropyl)-9a-aza-9a-homoerythromycin A:
.sup.1 H-nmr (CDCl.sub.3) delta 2.02
##STR5##
2.27 [6H, s, (CH.sub.3).sub.2 N--], 3.28 (3H, s, cladinose CH.sub.3 O--).
EXAMPLE 4
9-deoxo-9a-(beta-cyanoethyl)-9a-aza-9a-homoerythromycin A
9-deoxo-9a-aza-9a-homoerythromycin A (1.0 g) was dissolved in 10.0 ml of
acrylonitrile. The mixture was refluxed for 6 hours; then stirred
overnight at ambient temperature. The mixture was then concentrated in
vacuo to a tan foam. Chromatography of the crude product on silica gel (40
g; 70-230 mesh), eluting with a CH.sub.2 Cl.sub.2 /CH.sub.3
OH/concentrated NH.sub.4 OH=10/1/0.01 solvent mixture and monitoring
fractions by tlc (silica gel plates; CH.sub.2 Cl.sub.2 /CH.sub.3
OH/concentrated NH.sub.4 OH=6/1/0.1 eluting system; vanillin/H.sub.3
PO.sub.4 spray indicator with heat; R.sub.f =0.57), afforded 605 mg (56%
yield) of the title compound as a colorless foam.
.sup.1 H-nmr (CDCl.sub.3) delta 2.34 [6H, s, (CH.sub.3).sub.2 N--], 3.33
(3H, s, cladinose CH.sub.3 O--); .sup.13 C-nmr [CDCl.sub.3,
(CH.sub.3).sub.4 Si internal standard] ppm 177.62 (lactone>C.dbd.O),
118.85 (--C.tbd.N), 103.01 (C--1'), 95.91 (C--1"), 40.33 [(CH.sub.3).sub.2
N--]. EXAMPLE 5
9-deoxo-9a-(gamma-aminopropyl)-9a-aza-9a-homoerythromycin A
A solution of 47 g (59.6 mmole) of
9-deoxo-9a-(beta-cyanoethyl)-9a-aza-9a-homoerythromycin A in 520 ml of
ethanol was combined with 47 g of Raney-Ni catalyst (50% water-wet) and
hydrogenated on a Parr apparatus at 50 psi for 2.75 hours. Tlc inspection
(silica gel plates; elution with CHCl.sub.3 /CH.sub.3 OH/concentrated
NH.sub.4 OH=6/1/0.01; vanillin/H.sub.3 PO.sub.4 spray with heat) showed
the reaction to be incomplete. The mixture was charged with 25 g of fresh
catalyst, and hydrogenation at 50 psi (3.52 kg/cm.sup.2) was continued for
an additional 1.25 hours. The catalyst was filtered and the filtrate was
concentrated in vacuo to a colorless foam. The crude product was dissolved
in 600 ml of ethyl acetate. The solution was stirred with 800 ml of water
and the pH was adjusted to 9.5 with 6N sodium hydroxide. The organic phase
was dried over sodium sulfate and concentrated in vacuo to a foam.
Chromatography on silica gel (800 g, 70-230 mesh) eluting with CHCl.sub.3
/CH.sub.3 OH/concentrated NH.sub.4 OH=6/1/0.05; R.sub.f =0.15, afforded
14.7 g (31% yield) of the pure title compound as a colorless foam.
Crystallization of a 1.1 g sample from diethyl ether gave 545 mg of
colorless crystals; mp 180.degree.-183.degree. C.
.sup.1 H-nmr (CDCl.sub.3) delta 2.30 [6H, s, (CH.sub.3).sub.2 N--], 3.32
(3H, s, cladinose CH.sub.3 O--); .sup.13 C-nmr [CDCl.sub.3,
(CH.sub.3).sub.4 Si internal standard] ppm 177.01 (lactone>C.dbd.O),
102.69 (C--1'), 95.27 (C--1"), 40.33 [(CH.sub.3).sub.2 N--].
EXAMPLE 6
9,11-Deoxo-11beta,9a-(epoxypropano)-9a-aza-9a-homoerythromycin A [Formula
(I), n=3,4"-equatorial hydroxy] and
9-Deoxo-9a-(gamma-acetoxypropyl)-9a-aza-9a-homoerythromycin A
To a solution of 9-deoxo-9a-(gamma-aminopropyl)-9a-aza-9a-homoerythromycin
A (6.24 g, 7.90 mmoles) in 128 ml of chloroform, 1.01 g (1.16 ml; 8.63
mmoles) of isoamyl nitrite and 0.97 g (0.92 ml; 16.2 mmoles) of glacial
acetic acid were added, and the mixture was vigorously refluxed for one
hour. The mixture was stirred with 150 ml of water, and the pH adjusted to
8.0 with saturated aqueous sodium bicarbonate. The organic phase was
separated and washed with an equal volume of water, dried over sodium
sulfate, and concentrated in vacuo to a yellow foam. Tlc examination
showed two components in the crude product (silica gel plates momentarily
immersed in a 15:85 formamide/acetone solution and then air-dried; elution
with CHCl.sub.3 /acetone=1/1; vanillin/H.sub.3 PO.sub.4 spray with heat).
Formamide-treated silica gel was prepared by adding 360 ml of formamide to
a well-stirred 900 g silica gel (230-400 mesh)/1800 ml acetone slurry; and
then rotoevaporating solvent until a free-flowing powder was obtained. The
crude product (5.8 g) was chromatographed on the 900 g of
formamide-impregnated silica gel, eluting first with 2 liters of
CHCl.sub.3 /hexane=7/3; and then with 3 liters of CHCl.sub.3 /hexane=8/2.
The 5 ml fractions collected were tlc inspected utilizing the system
described above. Thus the two components produced in the reaction--the
(less polar) title compound (0.79 g, 13% yield), and
9-deoxo-9a-(gamma-acetoxypropyl)-9a-aza-9a-homoerythromycin A (0.76 g, 12%
yield)--were isolated as colorless amorphous solids.
9,11-Deoxo-11beta,9a-(epoxypropano)-9a-aza-9a-homoerythromycin A: .sup.1
H-nmr (CDCl.sub.3) delta 2.30 [6H, s, (CH.sub.3).sub.2 N--], 3.33 (3H, s,
cladinose CH.sub.3 O--); .sup.13 C-nmr (CDCl.sub.3) ppm 176.3
(lactone>C.dbd.O), 103.2 (C--1'), 96.2 (C--1"), 40.4 [(CH.sub.3).sub.2
N--]; mass spectrum (m/e) 616, 599, 458, 442, 158, 127.
9-Deoxo-9a-(gamma-acetoxypropyl)-9a-aza-9a-homoerythromycin A: .sup.1 H-nmr
(CDCl.sub.3) delta 2.01
##STR6##
2.29
##STR7##
3.31 (3H, s, cladinose CH.sub.3 O--); mass spectrum (m/e) 834.6.
EXAMPLE 7
9-Deoxo-9a-(cyanomethyl)-9a-aza-9a-homoerythromycin A 3',9a-bis-N-oxide
To a solution of 9-deoxo-9a-hydroxy-9a-aza-9a-homoerythromycin A
3'--N-oxide (11.0 g, 14.4 mmoles) in 138 ml of chloroform, 79 g (0.57
moles) of anhydrous potassium carbonate and 69 g (0.58 moles) of
bromoacetonitrile were added. The mixture was stirred at ambient
temperature for 5.25 hours. Tlc inspection [silica gel plates, elution
with CHCl.sub.3 /CH.sub.3 OH/concentrated NH.sub.4 OH=6/1/0.1;
vanillin/H.sub.3 PO.sub.4 spray with heat] showed consumption of starting
material and formation of a (less polar) product (R.sub.f =0.28) with only
trace amounts of impurities. The reaction was filtered and the filtrate
was concentrated in vacuo to a viscous oil. The oil was stirred with 600
ml of diethyl ether--affording a colorless granular solid which was
filtered and washed with 100 ml of ether prior to air-drying. The title
compound thus obtained (10.4 g, 89.9% yield, of colorless granular solid)
was used as is in the following Example.
EXAMPLE 8
9-Deoxo-9a-aza-9a-cyanomethyl-9a-homoerythromycin A
The title product of Example 7 (1.0 g), 10 ml of ethanol and 0.25 g of 5%
Pd on carbon was charged into a 50 ml Parr flask and the flask repeatedly
purged with nitrogen. It was then charged with hydrogen to 10 psi (0.70
kg/cm.sup.2) and hydrogenation carried out over a 4.5 hour period at room
temperature. The reaction was removed from the flask, filtered and
concentrated in vacuo to a foam. The foam was taken up in 100 ml of
methylene chloride, 100 ml water added and the pH brought to 9.5 by
addition of 6N NaOH. The methylene chloride layer was separated, dried
(Na.sub.2 SO.sub.4) and evaporated to dryness in vacuo to give 700 mg of a
foam. Chromatography on silica gel (21 g, 70-230 mesh), and elution with
CH.sub.2 Cl.sub.2 /MeOH/concentrated NH.sub.4 OH, 18/1/0.05 and
evaporation of the eluate afforded the title product (135 mg).
R.sub.f [silica gel plates, elution system CHCl.sub.3 /CH.sub.3
OH/concentrated NH.sub.4 OH=6/1/0.1; vanillin/H.sub.3 PO.sub.4 spray with
heat]=0.61.
.sup.1 H-nmr (CDCl.sub.3) delta 2.26 [6H, s, (CH.sub.3).sub.2 N--], 3.28
(3H, s, cladinose CH.sub.3 O--); .sup.13 C-nmr [CDCl.sub.3,
(CH.sub.3).sub.4 Si internal standard] ppm 178.0 (lactone>C.dbd.O), 116.76
(--C.tbd.N), 102.78 (C--1'), 95.16 (C--1"), 40.30 [(CH.sub.3).sub.2 N--].
EXAMPLE 9
9-Deoxo-9a-(beta-aminoethyl)-9a-aza-9a-homoerythromycin A
Sodium borohydride (1.17 g, 0.0309 mole) was added to a mixture of
9-deoxo-9a-cyanomethyl-9a-aza-9a-homoerythromycin A (2.4 g, 3.1 mmoles),
72 ml of methanol and anhydrous cobaltous chloride (0.792 g, 6.1 mmoles)
at room temperature. An exothermic reaction with much foaming occurred.
The mixture was stirred at room temperature for two hours and was then
concentrated under reduced pressure (aspirator) to a black oily residue.
The residue was taken up in 50 ml of 1:1 water:methylene chloride
solution, the pH adjusted to 2.5 by means of 1N HCl and the mixture
stirred for ten minutes. The aqueous phase was separated, 25 ml of
methylene chloride added and the pH adjusted to 9.5 by means of 1N NaOH.
The organic phase was then separated, an equal volume of water added and
the pH brought to 2.0 by addition of 1N HCl. Again the aqueous phase was
separated, 25 ml methylene chloride added, and the pH raised to 9.5 by
addition of 1N NaOH. The organic phase was separated, dried (Na.sub.2
SO.sub.4) and concentrated under reduced pressure to a white foam (1.15 g)
of crude title product.
Purification was accomplished by column chromatography of 1.05 g of crude
product on 30 g of 70-230 mesh silica gel and elution with CHCl.sub.3
:CH.sub.3 OH:NH.sub.4 OH (6:1:0.1) and collection of 5 ml fractions.
Fractions 80-150 contained the desired (more polar) material. They were
combined and concentrated to small volume under reduced pressure. The
concentrate was washed with saturated aqueous sodium bicarbonate solution,
dried (Na.sub.2 SO.sub.4) and evaporated in vacuo to a foam; 75 mg of
title product.
EXAMPLE 10
9,11-Deoxo-11beta,9a-(epoxyethano)-9a-aza-9a-homoerythromycin A
[Formula (I), n=2,4"-equatorial hydroxy]
A mixture of 9-deoxo-9a-(beta-aminoethyl)-9a-aza-9a-homoerythromycin A
(0.38 g, 0.488 mmole), chloroform (4 ml), isoamyl nitrite (0.072 ml, 0.536
mmole) and glacial acetic acid (0.056 ml, 0.976 mmole) was heated to
reflux for one hour. The addition of isoamyl nitrite and glacial acetic
acid was repeated and the mixture refluxed for two hours. It was cooled,
added to a mixture of 10 ml chloroform and 15 ml of saturated aqueous
sodium bicarbonate solution, and the pH adjusted to 9.5 by addition of 1N
NaOH. The organic phase was separated, dried (Na.sub.2 SO.sub.4) and
concentrated at reduced pressure to give 0.37 g of a tan foam. Column
chromatography on 55 g of formamide-treated silica gel (prepared as in
Example 3) using chloroform:hexane (90:10) as eluting agent and collection
of 5 ml fractions afforded the title product in fractions 81-130. The
combined fractions were washed with water, dried (Na.sub.2 SO.sub.4) and
concentrated under reduced pressure to a white solid. The solid was taken
up in methylene chloride, the solution filtered and evaporated in vacuo to
give 26.5 mg of product as a white solid.
.sup.13 C-nmr [CDCl.sub.3, chloroform internal standard] ppm 177.71
(lactone carbonyl), 103.36 (C--1'), 95.97 (C--1"), 40.40 [(CH.sub.3).sub.2
N--]; mass spectrum (m/e) 602, 444, 428.
EXAMPLE 11
9,11-Deoxo-11beta,9a-(epoxymethano)-9a-aza-9a-homoerythromycin A
[Formula (I), n=1,4"-equatorial hydroxy]
A solution consisting of 10.0 g (13.64 l mmole) of
9-deoxo-9a-aza-9a-homoerythromycin A, 1.19 g (1.10 ml, 14.0 mmoles) of 37%
aqueous formaldehyde, and 0.488 g (0.40 ml, 0.01 mole) of formic acid in
150 ml of chloroform was stirred at ambient temperature (ca. 25.degree.
C.) for 70 hours. Tlc inspection (silica gel plates; eluting with CH.sub.2
Cl.sub.2 /CH.sub.3 OH/concentrated NH.sub.4 OH=6:1:0.1; vanillin/H.sub.3
PO.sub.4 spray with heat) showed a complex mixture of at least five
components. The mixture was stirred with saturated aqueous sodium
bicarbonate (400 ml), and the pH of the aqueous layer was adjusted to 9.5
with 6N sodium hydroxide. The organic phase was separated, dried over
sodium sulfate, and concentrated in vacuo to a colorless foam. The crude
product was chromatographed on silica gel (405 g; 70-230 mesh; eluting
with CH.sub.2 Cl.sub.2 /CH.sub.3 OH/concentrated NH.sub.4 OH=12/1/0.05),
thus affording 563 mg (5.5% yield) of the pure title compound as a
colorless foam. R.sub.f (silica gel plates; CH.sub.2 Cl.sub.2 /CH.sub.3
OH/concentrated NH.sub.4 OH=6/1/0.1)=0.5.
.sup.13 C-nmr [CDCl.sub.3, (CH.sub.3).sub.4 Si internal standard] ppm
173.37 (lactone>C.dbd.O), 103,48 (C--1'), 97.07 (C--1"), 83.31 (C--5),
81.01
##STR8##
78.01, 76.11, 75.56, 40.24 [(CH.sub.3).sub.2 N--]; mass spectrum (m/e)
588, 571, 430, 414, 158, 127.
EXAMPLE 12
Following the procedures of Examples 7, 8 and 9, but using the appropriate
starting materials, the compounds tabulated below are prepared.
______________________________________
##STR9##
R.sub.1 4" -OH
______________________________________
CH.sub.2 CN axial and its 3', 9a-bis-Noxide
CH.sub.2 CH.sub.2 NH.sub.2
axial
______________________________________
EXAMPLE 13
Repetition of the procedure of Example 3 but using the 9a-beta-aminoethyl
derivative of Example 12 as reactant affords the 6-membered ring ether
derivative wherein the 4"--OH group has the axial configuration.
PREPARATION A
9-Deoxo-9a-aza-9a-hydroxy-9a-homoerythromycin A 3'--N-oxide
To a solution of 9-deoxo-9a-aza-9a-homoerythromycin A (10.0 g) in 40 ml of
methanol, a total of 50 ml of 30% aqueous hydrogen peroxide was added
dropwise while stirring over a 5-10 minute period. After stirring
overnight at ambient temperature, the reaction mixture was poured onto a
stirred slurry of ice (200 g), ethyl acetate (200 ml), and water (100 ml).
Excess hydrogen peroxide was quenched by cautious dropwise addition of
saturated aqueous sodium sulfite until a negative starch-iodine test was
indicated. The layers were separated; and the aqueous layer was washed
twice with 200 ml portions of ethyl acetate. The three organic extracts
were combined, dried over anhydrous sodium sulfate, and evaporated to
afford crude 9-deoxo-9a-aza-9a-hydroxy-9a-homoerythromycin A 3'--N-oxide
as a colorless foam (8.6 g).
While the crude product proved satisfactory for use in the preparative
procedure described below, purification was readily achieved by silica gel
chromatography, eluting with a methylene chloride: methanol:concentrated
ammonium hydroxide system (12:1:0.1). Progress of the column was followed
by thin layer chromatography on silica gel plates using the system
methylene chloride:methanol:concentrated ammonium hydroxide (9:1:0.1). The
plates were developed with a vanillin spray [ethanol (50 ml): 85% H.sub.3
PO.sub.4 (50 ml):vanillin (1.0 g)] indicator with heat. .sup.1 H-nmr
(CDCl.sub.3) delta 3.21
##STR10##
3.39 (3H, s, cladinose CH.sub.3 O--). MS: major peaks at m/e 576 (ion from
desosamine fragmentation), 418 (aglycone ion-minus both sugars). Both
peaks are diagnostic for
##STR11##
moiety within aglycone.
PREPARATION B
4"-Epi-erythromycin A Oxime
4"-Epi-erythromycin A (50 g, 0.0646 mole) was dissolved in 265 ml.
pyridine. Hydroxylamine hydrochloride (112.2 g, 1.615 mole) was added and
the slurry stirred 16 hours. The reaction mixture was stripped to a thick
slurry, diluted with 300 ml isopropanol, stirred well and filtered with
3.times.100 ml isopropanol for wash. The filtrate and washes were
combined, stripped to a water-soluble foam, and triturated with ether to
yield crude title product as the hydrochloride salt (100 g). The latter
was purified by distributing between CH.sub.2 Cl.sub.2 and aqueous
NaHCO.sub.3 adjusted to pH 9.5 with dilute NaOH. The aqueous layer was
separated and washed with ethyl acetate and then ether. All organic layers
were combined, dried (Na.sub.2 SO.sub.4) and stripped to yield title
product as a white foam, 5.95 g; tlc R.sub.f 0.5 (60:10:1 CH.sub.2
Cl.sub.2 :CH.sub.3 OH: concentrated NH.sub.4 OH); .sup.1 H-nmr
(CDCl.sub.3) delta 2.31 [6H, s, (CH.sub.3).sub.2 N--], 3.32 (3H, s,
cladinose CH.sub.3 O--).
PREPARATION C
4"-Epi-9a-aza-9a-homoerythromycin A
The title product of Preparation B (59.2 g, 0.0787 mole) was dissolved in
400 ml acetone. A slurry of NaHCO.sub.3 (60 g) in 225 ml H.sub.2 O was
added. Methanesulfonyl chloride (36.3 g, 24.5 ml) in 50 ml acetone was
added portionwise over 10 minutes, while maintaining the temperature less
than 30.degree. by means of a cooling bath. The mixture was stirred 4.5
hours, stripped of acetone, CH.sub.2 Cl.sub.2 (400 ml) added to the
aqueous residue, and the pH adjusted to 5.6 with 6N HCl. The aqueous layer
was separated, washed with two additional portions of CH.sub.2 Cl.sub.2
and then adjusted to pH 9.5 with 6N NaOH. The basic solution was extracted
2.times.fresh CH.sub.2 Cl.sub.2, 1.times.ethyl acetate and 1.times.ether.
The basic organic extracts were combined, dried (Na.sub.2 SO.sub.4) and
stripped to yield title product as an ivory foam, 41 g; tlc R.sub.f 0.4
(60:10:1 CH.sub.2 Cl.sub.2 :CH.sub.3 OH: concentrated NH.sub.4 OH); .sup.1
H-nmr (CDCl.sub.3) delta 2.27 [6H, s, (CH.sub.3).sub.2 N--], 3.29 (3H, s,
cladinose CH.sub.3 O--); .sup.13 C-nmr [CDCl.sub.3, (CH.sub.3).sub.4 Si
internal standard] ppm 177.24 (lactone>C.dbd.O), 163.53 (amide>C.dbd.O),
102.29 and 95.24 (C--3, C--5), 40.22 [CH.sub.3).sub.2 N--].
PREPARATION D
4"-Epi-9-deoxo-9a-aza-9a-homoerythromycin A
The title product of Preparation C (40 g) was dissolved 600 ml CH.sub.3 OH.
NaBH.sub.4 (45 g) was added over 45 minutes maintaining temperature less
than 38.degree.. The reaction mixture was stirred 64 hours, then stripped
to a thick slurry containing excess boro-hydride and boron ester complex
of product. The latter was distributed between 500 ml each CH.sub.2
Cl.sub.2 and H.sub.2 O, and the following sequence was repeated 3 times:
The pH was adjusted with stirring to constant pH 2.5 with dilute HCl; the
mixture was stirred vigorously 25 minutes; and the H.sub.2 O layer was
separated, combined with 500 ml fresh CH.sub.2 Cl.sub.2, adjusted to pH
9.5 with dilute NaOH and the CH.sub.2 Cl.sub.2 layer separated. The pH 9.5
CH.sub.2 Cl.sub.2 layer was combined with 500 ml fresh H.sub.2 O for
repetition of the sequence. On the third pass, the pH 9.5 CH.sub.2
Cl.sub.2 layer was dried (Na.sub.2 SO.sub.4) and stripped to yield crude
title product as a foam, 34 g, which was crystallized from 150 ml hot
isopropyl ether, cooled and diluted with 300 ml of pentane, affording
purified title product, 25.8 g; white crystals; tlc R.sub.f 0.5 (9:1
CHCl.sub.3 :diethylamine); R.sub.f 0.1 (90:10:1 CH.sub.2 Cl.sub.2
:CH.sub.3 OH: concentrated NH.sub.4 OH), mp 170.degree.-180.degree.;
.sup.1 H-nmr (CDCl.sub.3) delta 2.26 [6H, s, (CH.sub.3).sub.2 N--], 3.29
(3H, s, cladinose CH.sub.3 O--); .sup.13 C-nmr [CDCl.sub.3,
(CH.sub.3).sub.4 Si internal standard] ppm 179.44 (lactone>C.dbd.O),
103.57 and 96.70 (C--3, C--5); 41.50 [(CH.sub.3).sub.2 --N--].
PREPARATION E
4"-Epi-9-deoxo-9a-hydroxy-9a-aza-9a-homoerythromycin A 3'--N-Oxide
Stirring under N.sub.2, title product of Preparation D (3.0 g) was
dissolved in 15 ml of 1:1 THF:CH.sub.3 OH. Thirty percent H.sub.2 O.sub.2
(5 ml) was added. After 0.5 hour, additional 30% H.sub.2 O.sub.2 (2.5 ml)
was added. After a further 0.5 hour, the reaction mixture was cautiously
poured into 1:1 CH.sub.2 Cl.sub.2 :H.sub.2 O containing excess Na.sub.2
SO.sub.3 (exothermic). The pH was 9. The aqueous layer was washed with
fresh CH.sub.2 Cl.sub.2 and then ethyl acetate. The organic layers were
combined, dried (Na.sub.2 SO.sub.4) and stripped to yield title product,
2.7 g, tlc R.sub.f 0.15 (60:10:1 CH.sub.2 Cl.sub.2 :CH.sub.3
OH:concentrated NH.sub.4 OH); .sup.1 H-nmr (CDCl.sub.3) delta 3.21 [6H, s,
(CH.sub.3).sub.2 N.fwdarw.O], 3.38 (3H, s, cladinose CH.sub.3 O--); MS:
major peaks at m/e 576 (ion from desosamine fragmentation at C--5), 418
(N-hydroxyaglycone ion-minus | | |
