Enyne versus Diene RCM in the Synthesis of Cyclopentene Derivatives toward the A Ring of FR182877
作者:Jacques-Alexis Funel、Joëlle Prunet
DOI:10.1021/jo049557d
日期:2004.6.1
The A ring of FR182877, exemplified by ent-4-b,c, has been synthesized, involving an enyneRCM as the key step. A systematic comparison of enyne vs dieneRCM for the formation of cyclopentenederivatives showed that the latter metathesis proceeds much more easily even for this ring size.
Radical cyclization studies directed toward the synthesis of BMS-200475 ‘entecavir’: the carbocyclic core
作者:Frederick E Ziegler、Martha A Sarpong
DOI:10.1016/j.tet.2003.02.001
日期:2003.11
Two routes are presented for the conversion of d-diacetone glucose (5a) into a protected carbocycliccore of BMS-200475 (Entecavir). The reduction of two terminal epoxides with Cp2TiCl to form carbon radicals and their cyclizations with a terminal acetylene and an α,β-unsaturated ester lead ultimately to allylic alcohol 11a, a candidate for Mitsunobu coupling with guanine.
PREPARATION PROCESS OF AN ANTIVIRAL DRUG (ENTECAVIR) AND INTERMEDIATES THEREOF
申请人:Bartra Sanmartí Martí
公开号:US20130296558A1
公开(公告)日:2013-11-07
It comprises a preparation process of entecavir comprising: submitting a (1S,3R)-3-(tert-butyldimethylsilyloxy)-1-(oxiran-2-yl)pent-4-yn-1-ol (VIII) to a double esterification and to a radicalary cyclization, yielding a compound of formula (V), where either a compound of formula (VIII) is submitted to a first esterification reaction, then to a catalytic radicalary cyclization using titanocene dichloride as catalyst in the presence of Mn/2,4,6-collidine HCl or Zn/2,4,6-collidine/trimethylsilyl chloride, and finally to a second esterification reaction or, alternatively, the compound of formula (VIII) is submitted first to a catalytic radicalary cyclization, and then to an esterification reaction. Entecavir can be obtained by submitting compound (V) to a desilylation reaction to remove the TBS group and then to a Mitsunobu coupling with 2-amino-6-chloroguanine, followed by hydrolysis. It also relates to some new intermediates of the process.