| Research Abstract |
Widespread use of homoehiral 1,2-diaryl-1,2-diaminoethanes and 2-amino-1,2-dimylethanols as chiral auxiliaries coupled with difficulties associated with their preparation prompted us to investigate new methodologies for their syntheses. For the preparation of this highly useful class of compounds, enantioselecive imino pinaeol coupling of p-anisylbenzd-imine was investigated using Zn-Cu couple in the presence of (+)-camphorsulfonic acid as a chrial auxiliary to give (R,R)-1,2-diphenylethylemtediamine derivative in high enantiomeric purity. Highly enantioselective reduction of 1,2-bis(p-methoxyphenylimino)- 1,2-diphenylethmte was also conducted with 0.5 mo1% of new oxazaborolidine, derived from L-thronine and a stoichiomebic amount of BH_3THF, to give 1,2-diphenylethylenediamine derivative in excellent enantiomeric purity. The subsequent deportation of nitrogen atoms afforded (R,R)-1,2-diphenylethylenediamine in enantiomerically pure form. Moreover, the reduction of 1,2-diaryl-2-benzylo
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xyhnhtoethanones conducted using the above oxazaborolidine and BH_3 Sme_2 gave beta-imino alcohols chemoselectively in high enantiomeric purity. Subsequent selective reduction of the imino functionality affords either .syn- or anti-2amino-1,2-diarylethanols in high enantomeric purity by choosing appropriate reduction conditions. Highly diastereo- and enantioselective reduction of 1,3-diketones was also conducted using the same oxazaborolidine and borane-THF complex in THF to give 1,3-diols in high enamctiomeric purity. In particular, the reduction of cyclopentane or cyclohexan- 1,3-dione derivatives gave chiral 1, 3-diols it excellent enantiomericexcess without formation of mc.vo-compounds. Moreover, enantioselective reduction of meso-imide was conducted under essentially same conditions to give hydroxy lactams in highenantiomeric purity. In particular, the reduction of the mes-imide posssesing an imidazolidinone ring gave the hydroxy lactam with high enatiomeric purity. The hydroxy lactam thus obtained was successfully transfotmed into (+)-biotin. Less
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