Highly enantioselective syntheses of anti homoaldol products by (-)-sparteine-mediated lithiation/transmetalation/substitution of N-Boc allylic amines

[GRAPHICS] (-)-Sparteine-mediated lithiation/transmetalation/substitution of N-Boc all ylic amines provides anti-configured homoaldol precursors in yields of 38-8 5% and enantiomeric ratios of 83:17-99:1. Subsequent O-protection and hydro lysis allows access to O-protected homoaldol adducts in good yields. The ab solute configurations of the homoaldol products have been assigned by calcu lation of optical rotations and by X-ray crystallography of derivatives. A stereochemical course of reaction for the lithiation/transmetalation/substi tution sequence is proposed.