A stereocontrolled alkylation of chiral pyridinium salts with Grignard reagents: synthesis of (+)-normetazocine and (+)-nordextrorphan
摘要:
The synthesis of chiral pyridinium salts 3, bearing lipophilic counteranions, is described. These salts, soluble in THF or toluene, undergo nucleophilic alkylation with benzylic Grignard reagents to give, after reduction of the unstable dihydropyridine intermediates, adducts 4 with regio- and stereoselective attack at position 2, the observed stereoselectivity ranging from 8:1 to 12.5:1. These results allowed an asymmetric synthesis, following Grewe's route, of (+)-normetazocine and (+)-nordextrorphan, key precursors of various benzomorphan or morphinan drugs.
A stereocontrolled alkylation of chiral pyridinium salts with Grignard reagents: synthesis of (+)-normetazocine and (+)-nordextrorphan
摘要:
The synthesis of chiral pyridinium salts 3, bearing lipophilic counteranions, is described. These salts, soluble in THF or toluene, undergo nucleophilic alkylation with benzylic Grignard reagents to give, after reduction of the unstable dihydropyridine intermediates, adducts 4 with regio- and stereoselective attack at position 2, the observed stereoselectivity ranging from 8:1 to 12.5:1. These results allowed an asymmetric synthesis, following Grewe's route, of (+)-normetazocine and (+)-nordextrorphan, key precursors of various benzomorphan or morphinan drugs.
A stereocontrolled alkylation of chiral pyridinium salts with Grignard reagents: synthesis of (+)-normetazocine and (+)-nordextrorphan
作者:Yves Genisson、Christian Marazano、Bhupesh C. Das
DOI:10.1021/jo00060a019
日期:1993.4
The synthesis of chiral pyridinium salts 3, bearing lipophilic counteranions, is described. These salts, soluble in THF or toluene, undergo nucleophilic alkylation with benzylic Grignard reagents to give, after reduction of the unstable dihydropyridine intermediates, adducts 4 with regio- and stereoselective attack at position 2, the observed stereoselectivity ranging from 8:1 to 12.5:1. These results allowed an asymmetric synthesis, following Grewe's route, of (+)-normetazocine and (+)-nordextrorphan, key precursors of various benzomorphan or morphinan drugs.