A pyranoindolizine derivative represented by the following general formula (I): ##STR1## wherein R means a hydrogen atom or hydroxyl group and Q denotes >C.dbd.O or ##STR2## with a proviso that Q is other than >C.dbd.O when R is a hydrogen atom. Its preparation process is also described.
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated
As part of our attempts to employ the unnatural (R)-type compound (8), which was produced by optical resolution of the pyranoindolizine 6, in the synthesis of natural (20S)-camptothecin, inversion of the configuration at the tertiary alcohol of the (4R)-pyranoindolizine 11 to give the (4S)-isomer 14 was achieved in 33% yield via the methanesulfonate 12.
Formal total synthesis of camptothecin via ring-closing metathesis strategy
作者:Subhash P. Chavan、K. Pasupathy、M.S. Venkatraman、Ramesh R. Kale
DOI:10.1016/j.tetlet.2004.07.101
日期:2004.9
A formaltotalsynthesis of camptothecin 1 is presented. The key steps include construction of the D-ring of camptothecin featuring an efficient ring-closing metathesis (RCM) reaction and the subsequent Michael addition of nitropropane across the double bond of the dihydropyridone 3.