Carbocyclische Verbindungen aus Monosacchariden. I. Umsetzungen in der glucosereihe

Carbocyclic Compounds from Monosaccharides. 1. Transformations in the Glucose Series A method for the preparation of pentasubstituted cyclopentanes from monosaccharides is presented, involving two crucial steps, viz. the reductive fragmentation of 5‐bromo‐5‐deoxyglucosides (such as 10, 17 and 23 , see Scheme 3 ) with Zn or butyl lithium yielding 5,6‐dideoxy‐hex‐5‐enoses (such as 11 and 24 , see Schemes 3 and 4 ), and the subsequent cyclization of these hexenoses with N ‐methyl‐ or N ‐(alkoxyalkyl)hydroxylamines ( via the corresponding nitrones) to form cyclopentano‐isoxazolidines (see Scheme 2 ). Thus, the glucosides 17 and 23 were converted diastereoselectively and in good yields into the cyclopentano‐isoxazolidines 27 and 45 ( Schemes 5 and 7 ), which were characterized by their transformation into various derivatives. 27 and 45 were correlated through the common derivative 62 . The configuration of the cyclization products were established by pyrolysis of the N ‐oxide 65 to the enol ether 67 ( Scheme 10 ).