Asymmetric nitrone-vinyl sulfoxide cycloadditions: a highly enantioselective synthesis of (+)-sedridine
作者:Chantal Louis、Claude Hootelé
DOI:10.1016/0957-4166(95)00287-y
日期:1995.9
Cycloaddition of 2,3,4,5-tetrahydropyridine-1-oxide 1 to (Z)-(R)-vinyl sulfoxides 2a-d proceeds in high yield to give isoxazolidines 3a-d and 4a-d with complete exo selectivity and with 82–98% asymmetricinduction. This method provides an efficient synthesis of the enantiomerically pure piperidine alkaloid (+)-sedridine 6a.
The palladium catalyzed [3+2] cycloaddition of trimethylenemethane with a variety of vinylsulfoxides led to cycloadducts in good to excellent chemical yields and with a good level of asymmetricinduction.
The cycloaddition of (Z) and (E)-vinyl sulfoxides with cyclic nitrones 1 and 2 is reported. Best diastereoselection is achieved with (Z)-vinyl sulfoxides 7a-d as dipolarophiles. This methodology allows the highly stereoselective synthesis of (+)-sedridine 9a, (-)-hygroline 10 and (-)-(2S)-N-carbomethoxypelletierine 11a. (C) 1997, Elsevier Science Ltd. All rights reserved.