Enantioselective deprotonation of 8-oxabicyclo[3.2.1]octan-3-one systems using homochiral lithium amide bases
作者:Barry J. Bunn、Paul J. Cox、Nigel S. Simpkins
DOI:10.1016/s0040-4020(01)80520-2
日期:1993.1
The asymmetric transformation of oxabicyclic ketones 6 and 7 into non-racemic enol silanes 12 (88% ee) and 10 (85% ee), respectively, was achieved using the homochiral lithiumamide base 4. Conversion of 10 into a known key intermediate 15 for C-nucleoside synthesis was possible in a highly efficient two step sequence.
A new synthetic approach to the polyoxins: Concise stereoselective preparation of protected thymine polyoxin C
作者:David M. Gethin、Nigel S. Simpkins
DOI:10.1016/s0040-4020(97)00935-6
日期:1997.10
A new approach to the synthesis of thymine polyoxin C has been devised, which uses the prochiral ketone 8-oxabicyclo[3.2.1]octan-3-one 8 as the starting material. An enol silane 12 derived from this ketone was reacted with TsN=Se=NTs in order to install the nitrogen functionality required in die final product whilst retaining a reactive C=C in the product 13. This compound was cleaved using ozone lid, following protecting group manipulation, was subjected to an unusual one carbon side-chain degradation employing Pb(OAc)(4) to give an appropriate glycosyl donor 25. Completion of the synthesis of a protected thymine polyoxin C was then carried out by reaction of 25 under Vorbruggen conditions. (C) 1997 Elsevier Science Ltd.