反应详情

A process for converting 5-(t-BOC)amino-5-deoxy-l,2 O-isopropylidene-α-D-glucuronolactone to castanospermine which comprises (a) reacting 5-(t-BOC)amino-5-deoxy-l,2-O?isopropylidene-α-D-glucuronolactone (I) with ethyl acetate and a strong base in an inert solvent at low temperature whereby the ethyl acetate adds across the carbonyl group of the lactone to give the corresponding cyclic hemiketal of a β-keto ester (II); (b) hydrogenating the hemiketal catalytically under pressure over a platinum catalyst in ethyl acetate to reduce the β-keto function and give β-hydroxy ester (III); (c) treating the β-hydroxy ester with formic acid in an inert solvent with cooling to remove the protecting group from the amine followed by basification to provide internal cyclization of the amine to give lactam (IV); (d) reducing the lactam with an aluminum hydride reducing agent to give the corresponding pyrrolidine (V); and (e) treating the pyrrolidine first with trifluoroacetic acid with cooling and then hydrogenating over platinum catalyst under pressure to give castanospermine (VI).