A process for the stereospecific synthesis of [E] alkenes from enamines comprising the steps of hydroborating the enamine; esterifying the organoborane so formed and oxidizing the boronic ester in the presence of hydrogen peroxide and in the absence of added base under conditions sufficient to form the [E] alkene in high yield.
The present invention relates to novel, powerful reducing agents, lithium aminoborohydrides which are prepared by addition of BH.sub.3 .cndot.THF to the corresponding dialkylamine at 25.degree. C. to give the intermediate amineborane complex. Subsequent deprotonation by strong base, e.g. n-BuLi, yields the aminoborohydride quantitatively. Lithium aminoborohydrides are powerful reducing agents, comparable in strength to lithium aluminum hydride. The activity is determined by the dialkylamine. Lithium pyrrolidinoborohydride has unique activity and selectivity in its reducing properties. Esters, lactones and anhydrides are reduced cleanly at 25.degree. C. to give the corresponding alcohols, while carboxylic acids are not reduced. Test reductions show that lithium pyrrolidinoborohydride is also capable of reducing a wide range of functional groups including amides, epoxides, oximes, nitriles and halides.
The present invention relates to a process for the synthesis of chiral enantiomerically pure .beta.-amino alcohols which are extraordinarily important as therapeutic agents for the treatment of a variety of human disorders and as chiral auxiliaries in organic synthesis. The hydroboration of enamines is a versatile and convenient method for the synthesis of both racemic and enantiomerically pure .beta.-amino alcohols in high yields. This methodology enables the synthesis of virtually any .beta.-amino alcohol. Hydroboration of these enamines with chiral organic borohydrides, e.g. either mono- or diisopinocampheylborane, followed by oxidation with aqueous or solid NaOH/30% H.sub.2 O.sub.2 or Me.sub.3 NO, gives the corresponding chiral .beta.-amino alcohol. Enantiomeric excesses ranged from 60% for reactions run at 25.degree. C. to greater than 99% for reactions run at -25.degree. C.
The invention discloses materials that adsorb readily to the surfaces of body tissues in situ and provide a steric barrier between such tissues, so that tissue adhesions, which typically form following surgical procedures, are minimized. These materials contain a polymer of hydrophilic molecules such as polyethylene glycol (PEG) bound to a polymer that spontaneously adsorbs to biological tissue such as phenylboronic acid (PBA). The PEG-PBA co-polymer can be formed in a variety of geometries. The materials can also be used to coat prosthetics and other implants.
The invention discloses materials that adsorb readily to the surfaces of body tissues in situ and provide a steric barrier between such tissues, so that tissue adhesions, which typically form following surgical procedures, are minimized. These materials contain a polymer of hydrophilic molecules such as polyethylene glycol (PEG) bound to a polymer that spontaneously adsorbs to biological tissue such as phenylboronic acid (PBA). The PEG-PBA co-polymer can be formed in a variety of geometries. The materials can also be used to coat prosthetics and other implants.
