Double stereodifferentiation in aldol reactions on protected pyroglutamateesters

Excellent stereoselectivity is observed at both chiral centres created in t he aldol condensation of the matched pairs of (2S)-pyroglutamate ester uret hane 1 and either (R)-glyceraldehyde acetonide 2 or the (S)-Garner aldehyde 6. Stereoselectivity was not so impressive with the mismatched pairs 1+4 o r 1+8 or when the C-2 reduced bromide 12 was used in the corresponding reac tion with aldehyde 2. (C) 2001 Elsevier Science Ltd. All rights reserved.