A protocol is presented for a completely enantioselective for-sunobu trick"). Its application to the unprecedented synthesis of enantiopure cis-3,4-dihydroxypyrroline N-oxides, em-mal desymmetrization of C s -symmetric diols by monoprotection of the corresponding enantiopure C 2 diols, followed by ployed in the enantiodivergent synthesis of two selectively protected 1,2,7-trihydroxyindolizidines, is also reported. an inversion of configuration by a Mitsunobu reaction ("Mit-A route of easy access to enantiopure hydroxypyrroline of optically pure nitrones 3, [4] based on a general strategy which might present an alternative to the desymmetrization N-oxides 1 (Scheme 1), together with their straightforward application to the synthesis of polyhydroxy indolizidine [1] of meso-diols. This process is generally accomplished by the selective derivatization of a single hydroxy group in the C s -and pyrrolizidine [2] alkaloids and their unnatural congeners, was recently reported.
symmetric diols by means of enzymatic catalysis ("meso trick"). [5] [6] We now propose a route of access to the same Scheme 1. Retrosynthetic analysis for monohydroxy-and transselectively protected enantiopure cis-diols by means of a and cis-dihydroxypyrroline N-oxides