Diastereoselection of the addition of silyloxyfurans to five-, six- and seven-membered N-acyliminium ions
摘要:
The addition of silyloxyfuran 1a to five-, six- and seven-membered N-acyliminium ions 2 afforded threo-3 as the major isomers (the structures of 3a, 3g and 3m were determined by X-ray analysis). The diastereoisomeric ratio increased with bulkier carbamate groups (Boc>Cbz>CO2Me) with the five- and seven-membered N-acyliminium ions more selective than the six-membered ones. However. erythro-4 isomers predominated when 5-methylsilyloxyfuran 1b was employed (the structures were determined by NOE studies on the corresponding bicyclic lactams 6a.b and 7a,b) and the formation or regioisomer 5 was observed for N-acyliminium ions with Boc (seven-membered series) and Cbz (six- and seven-membered series) groups. (C) 2001 Elsevier Science Ltd. All rights reserved.
Diastereoselection of the addition of silyloxyfurans to five-, six- and seven-membered N-acyliminium ions
作者:Maria da Conceição F de Oliveira、Leonardo Silva Santos、Ronaldo Aloise Pilli
DOI:10.1016/s0040-4039(01)01388-0
日期:2001.10
The addition of silyloxyfuran 1a to five-, six- and seven-membered N-acyliminium ions 2 afforded threo-3 as the major isomers (the structures of 3a, 3g and 3m were determined by X-ray analysis). The diastereoisomeric ratio increased with bulkier carbamate groups (Boc>Cbz>CO2Me) with the five- and seven-membered N-acyliminium ions more selective than the six-membered ones. However. erythro-4 isomers predominated when 5-methylsilyloxyfuran 1b was employed (the structures were determined by NOE studies on the corresponding bicyclic lactams 6a.b and 7a,b) and the formation or regioisomer 5 was observed for N-acyliminium ions with Boc (seven-membered series) and Cbz (six- and seven-membered series) groups. (C) 2001 Elsevier Science Ltd. All rights reserved.