Carbohydrate-like chiral synthons: Synthesis of the N-trifluoroacetyl derivatives of 4-amino-2,4,6-trideoxy- l- lyxo-, - l- arabino, and - l- ribo-hexose from the (2 S,3 R)-2,3-diol formed from cinnamaldehyde in fermenting baker's yeast

Abstract

(2 S,3 S)-2,3-Isopropylidenedioxybutyraldehyde, produced by ozonolysis of the O-isopropylidenated (2 S,3 R)-2,3-diol formed from cinnamaldehyde in fermenting baker's yeast, affords, with diallyl-zinc, the C 7, carbohydrate-like, noncarbohydrate-derived adduct (2 S,3 R,4 R)-2,3-isopropylidenedioxy-4-hydroxyhept-6-ene ( 9). This material is a stereochemically defined, functionalised, chiral synthon which is useful in the synthesis of enantiomerically pure products. The synthesis of the N-trifluoroacetyl derivatives of 4-amino-2,4,6-trideoxy- l- lyxo ( 21), - l- arabino ( 22), and - l- ribo-hexose ( 23) from 9 is reported. Key intermediates in the synthesis were the isomeric epoxy alcohols (2 S,3 S,4 S)-3,4-epoxyhept-6-en-2-ol, (2 S,3 R,4 S)-2,3-epoxyhept-6-en-4-ol, and (2 S,3 R,4 R)-2,3-epoxyhept-6-en-4-ol. The nitrogen function is introduced by intramolecular epoxide-opening of the corresponding benzyl urethanes which gave, eventually, (2 S,3 R,4 S)-3- N-trifluoroacetamidohept-6-en-2,4-diol, (2 S,3 S,4 S)-3- N-trifluoroacetamidohept-6-en-2,4-diol, and (2 S,3 S,4 R)-3- N-trifluoroacetamido-6-en-2,4-diol, from which the required C 6-N frameworks of 21–23 were obtained by ozonolysis.