ORGN 369 |
| The OsO4-catalyzed dihydroxylation reaction of allylic amino olefins is one of the most simple and efficient methods to produce a vicinal amino diol moiety which occurs abundantly in many biologically active natural products. In spite of its usefulness, the stereoselective dihydroxylation reaction of allylic amines has not been studied as much as that of allylic alcohols. Often, the poor or inconsistent stereochemical results have been reported for acyclic allylic amino derivatives with flexible conformation. In several cases, even the well-established Sharpless asymmetric dihydroxylation reactions resulted in the mixed results. In this presentation, a highly anti-selective dihydroxylation method for 1,2-dialkyl substituted (Z)-allylic amines is reported. In general, the OsO4-catalyzed dihydroxylation reactions of N-Boc-1,2-dialkyl substituted (Z)-allylic amines have been known to give the syn diol with regard to the amino group. We have found that further protection of the N-Boc-1,2-dialkyl substituted (Z)-allylic amines with another Boc group into an N,N-diBoc group resulted in the opposite anti diol in the OsO4-catalyzed dihydroxylation reactions. Among the reaction solvents, the higher anti selectivity (>10:1) was shown in CH2Cl2. With the above results in hand, an efficient and stereoselective synthesis of D-ribo-phytosphingosine was achieved. The results should be useful to produce many biologically active compounds, natural or unnatural, with the amino diol or related functionalities reliably in a stereoselective manner.
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Asymmetric Reactions and Syntheses
1:00 PM-5:00 PM, Tuesday, March 27, 2007 McCormick Place East -- Room E351, Level 3, Oral
Division of Organic Chemistry |
