Steroid 20, 2 1-glyoxals reacted selectively at C-2 1 with N-monosubstituted ethanolamines giving moderate yields of oxazolidines which appear to be mixtures of Czl epimers. N- Methyloxazolidines were obtained simply by heating the glyoxal in a solvent with 2 to 5 molar equivalents of substituted ethanolamine at 50 to 100'for 1-2 hr. The N- methyloxazolidine obtained from prednisolone 21-aldehyde was more active than ...