Taxoids, rearrangement

A C-11,12 double-bond rearranged product 24 was observed when 2, 7-deacetyl paclitaxel was treated with Yarovenko reagent (Et2NCF2CHFCl), which can be then transformed into 2 -Troc-10-deoxy paclitaxel (25) by catalytic hydrogenation, along with the formation of a small amount of 12-fluorinated 26. All taxoids, after deprotection, showed reduced cytotoxicity seven to eight times. 

A number of taxoids isolated from different Taxus species, on structural reinvestigation were found to contain a rearranged nortaxoid skeleton or 11(15—>V)-abeo taxoids, as they are more correctly described (133,160,161) and not a taxane skeleton as originally proposed. Brevifoliol (181) was the first natural taxoid with 11(15—>l)-afoeotaxane skeleton which was initially assigned a normal taxane skeleton (162) but was later corrected to the... 

The only known taxoid with 11( 15—> 1), 11( 10— >9) bisabeotaxane skeleton is wallifoliol (232) from T. wallichiana (134). A benzil-benzilic acid type rearrangement of 10-dehydro-10-deacetyl-ll(15—>l)-abeobaccatin 111 (A) might be the biosynthetic pathway of this compound. 

Appendino G, Varese M, Gariboldi P, Gabetta B (1994) The Chemistry (15) and Occurrence of Taxane Derivatives. XV. A New Rearrangement of Oxetane-Type Taxoids. Tetrahedron Lett 35 2217... 

Hu S, Sun D, Tian X, Fang Q. Selective microbial hydroxyl-ation and biological rearrangement of taxoids. Tetrahedron Lett. 1997 38 2721-2724. 

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