1,3-heterazolidin-2-ones as starting materials for optically active 1,3,2-oxazaborolines and 1,3,2-diazaboroline derived from ephedrines

(4R,5R)-3,4-Dimethyl-5-phenyl-1,3,2-oxazaboroline (1a) derived from pseudoephedrine and (4R,5S)-1,3,4-trimethyl-5-phenyl- 1,3,2-diazaboroline (1d) derived from ephedrine have been prepared from the corresponding 1,3-heterazolin-2-one. Hydrolysis of 1d afforded the 1-methyl-3-(methylamine)-2-phenyl-propylamine 5. The structures were established from H-1,C-13 and B-11 NMR data. The X-ray diffraction analysis of (4R,5S)-(+)-3,4-dimethyl-5-phenyl-1 -hydro-1,3-diazolidine-2-one (4e) was performed. Isomeric N-monoborane adducts of the 1,3,2-diazaboroline 1d were prepared, and their structures were deduced from the NMR data. (C) 1998 Elsevier Science Ltd. All rights reserved.