A. Volonterio, P. Bravo*, S. Capelli
Mar 10, 1997
Citations
0
Influential Citations
11
Citations
Journal
Tetrahedron Letters
Abstract
Abstract The chiral non racemic N -Cbz-trifluoropyruvaldehyde- N , S -ketal 1a (enantiomeric excess up to 74%) is a new trifluoro 3-C building block, which has been reacted with several Grignard reagents, stereoselectively affording the corresponding secondary carbinols 2 . The N , S -ketal stereocentre, whose absolute stereochemistry has been determined by X-ray analysis of the α-phenylpropionate 3 , is able to provide excellent stereocontrol. Highly stereoselective p -tolylthio group displacement afforded the N -Cbz-phenyl derivative 2d , transformed into trifluoro-norephedrine (S,S)- 5 and -ephedrine (S,S)- 6 .