Synthesis and epimerization of 10-N-(6-deoxy-1,2 : 3,4-di-O-isopropylidene-alpha-D-galactopyranos-6-yl)-(11aS)-pyrrolo[2,1-c][1,4]benzodiazepin-5,11-dione

The reaction of the 1.,2:3,4-di-O-isopropylidene-6-O-tosyl-alpha -D-galacto pyranose 2 with (11aS)-pyrrolo[2,1-c][1,4]benzodiazepin-5.11-dione 1. prepa red front L-proline and isatoic anhydride, gave two products which were pre viously reported as conformational isomers. In this work. an X-ray crystall ographic study showed these to be the diastereomeric pair (HaS)- and (11aR) -10-N-(6-deoxy-1.2:3.4-di-O-isopropylidene-alpha -D-galactropyranos-6-yl)-p yrrolo[2,1-c,][1,4]benzodiazepin-5.11-diones as a consequence of C(11a) epi merization in the benzodiazepine moiety during glycosylation under basic re action conditions, The hydrosolubility of the deprotected products ere comp ared with those of the analogous benzodiazepine derivatives. (C) 2001 Elsev ier Science Ltd. All rights reserved.