A tandem radical macrocyclisation - radical transannulation strategy to the taxane ring system
作者:Stephen A. Hitchcock、Gerald Pattenden
DOI:10.1016/s0040-4039(00)61300-x
日期:1992.8
Treatment of the iodo-trienone (8 b) with tri-n-butyltin hydride in the presence of AIBN is shown to produce the taxane ring system (11) by way of a tandem radical macrocyclisation - radical transannulation sequence, i.e. (8 b) → (9) → (11) (cf. Scheme 1).
A tandem radical macrocyclisation-transannular cyclisation approach towards the taxanes
作者:Stephen A. Hitchcock、Stephen J. Houldsworth、Gerald Pattenden、David C. Pryde、Nicholas M. Thomson、Alexander J. Blake
DOI:10.1039/a805268i
日期:——
Separate treatment of the iodotrienedione 19 and the iododienynedione 38 with Bu3SnH–AIBN produces the corresponding taxane ring systems 25 (25–30%) and 56 (50–60%) respectively by way of tandem radical macrocyclisation-radical transannular cyclisations. By contrast the analogous iodopolyenones 61, 63, 65a, 66a, 86a and 87a, together with the corresponding iodoenynones 39a and 59 failed to undergo similar tandem radical reactions, and instead gave products resulting from direct reduction of the carbon–iodine bonds in these substrates. The structures of the taxane analogues 25 and 56 followed from analysis of their NMR spectroscopic data and comparison with similar NMR data for related taxoids described in the literature. The stereochemistry of 56 was secured from an X-ray crystal structure determination of the 1,5-diol 57 produced from reduction of 56 with DIBAL.