Highly Diastereoselective Synthesis of 2-Oxazoline-4-carboxylates by Formal Cycloadditions of a 5-Alkoxyoxazole with α-Alkoxy Aldehydes Catalyzed by Tin(IV) Chloride

Article abstract of DOI:10.1021/jo00091a023

The formal <3 + 2> cycloaddition of 5-methoxy-2-(p-methoxyphenyl)oxazole with 2(S)-(benzyloxy)propanal and 2(S)-<(tert-butyldimethylsilyl)oxy>propanal in the presence of tin(IV) chloride gave cis-(4R,5S,1'S)- and trans-(4S,5S,1'S)-5-(1'-alkoxyethyl)-4-(methoxycarbonyl)-2-(p-methoxyphenyl)-2-oxazolines with high diastereoselectivity (94 and 92percent selectivity, respectively).A similar reaction of 5-methoxy-2-(p-methoxyphenyl)oxazole with 2,3-di-O-benzyl-D-glyceraldehyde gave methyl cis-(4S,5R,1'R)-2-(p-methoxyphenyl)-5-<1',2'-bis(benzyloxy)ethyl>-2-oxazoline-4-carboxylate with high diastereoselectivity (>95percent selectivity), and the latter was easily converted to biologically important chiral 2-amino-1,3,4,5-tetrol derivatives.