Preparation of N-arylmethyl aziridine derivatives, 1,4,7,10-tetraazacyclododecane derivatives obtained therefrom and N-arylmethyl-ethanol-amine sulphonate esters as intermediates
Aziridines may be subjected to a cyclooligomerization reaction to produce polyazacycloalkane compounds useful for example in the preparation of chelating agents for use in diagnostic imaging contrast agents. N-benzyl-aziridine in particular is useful as it can be cyclotetramerized and debenzylated to yield cyclen, a key intermediate in chelating agent preparation. The invention provides a particularly attractive route to production of N-benzyl and other N-arylmethyl aziridines of formula (I) where each R.sub.1 is independently hydrogen or a group AR and Ar is an optionally substituted phenyl group. The process comprises reacting a purified N-arylmethylethanolaminesulphonate ester with a base. N-arylmethyl-ethanolamine sulphonate ester of the formula R'NHCH.sub.2 CH.sub.2 OSO.sub.3 H, wherein the N-arylmethyl group R' is an N-(bisarylmethyl) or N-(triarylmethyl) group, as intermediates. In a further aspect, the invention provides compounds of formula (II) ##STR1## where Ar and R.sub.1 are as hereinabove defined and at least two differing ArCHR.sub.21 moieties are present.
Left and right video cameras 18L and 18R are disposed on both sides of a front video camera 18M. Solid-pictorial video signals used upon signal transmission are generated by using video signals outputted from the left and right video cameras with respect to a video signal outputted from the front video camera. The left and right video cameras make use of simplified video cameras and are cameras with no zoom functions or the like. The video signals obtained from the left and right video cameras are used as signals for forming a solid picture. In the present example, only solid information with respect to a main picture is transmitted as a video signal to reduce the amount of transmission. Since a motion-compensated DCT encode process using the front video signal as a reference picture is performed to extract only the video signal having the solid information from the left and right video signals. Since the simplified video cameras can be utilized, solid-pictorial video signals can be generated at low cost.
