ENANTIOSPECIFIC AND DIASTEREOSELECTIVE SYNTHESIS OF ANTI α-HYDRAZINO- AND α-AMINO-β-HYDROXYACIDS THROUGH "ELECTROPHILIC AMINATION" OF β-HYDROXYESTERS

Article abstract of DOI:10.1016/S0040-4020(01)86060-9

β-Hydroxyesters 1a-d were transformed into corresponding dianions and condensed with di-t-butylazodicarboxylate to give anti protected α-hydrazino-β-hydroxyesters 2a-d with good diastereoselectivities (up to 94:6).Cleavage of protecting groups followed by ester hydrolysis gave the previously unknown anti α-hydrazino-β-hydroxyacids 4a-d, which were in turn converted by hydrogenolysis into anti α-amino-β-hydroxyacids 5a-d.Starting from (S) 1a, enantiomerically pure (2S,3S) allo-threonine 5a was obtained in good overall yields.On the contrary, reaction of silyl ketene acetal 10, derived from 1a, with a diazonium salt furnished predominantly the syn isomer, but in unsatisfactory yield.