ON THE STERIC COURSE OF ADDITION OF GRIGNARD REAGENTS ONTO α,β-DIALKOXY ERYTHRO AND THREO CHIRAL ALDEHYDES. SYNTHESIS OF (+) AND (-)-EXO AND ENDO-BREVICOMIN

Article abstract of DOI:10.1016/S0040-4039(01)82054-2

Addition of BrMgCH2CH3 onto the erythro and threo aldehydes (1) and (2) to form (3)+(6) and (9)+(10) proceeds with 6:4 and 8:2 threo-erythro selectivity, respectively.From (3) and (6), (2S) and (2R)-2-benzyloxy butyraldehyde (13) and (14) have been prepared.Addition of ClMgCH2CH2CH2(COCH2CH2O)CH3 onto (13) and (14) proceeds with 6:4, threo-erythro selectivity, to give after preparative gas chromatographic separation, the enantiomeric forms of exo- and endo-brevicomin (19), (21) and (20), (22).