Effi cient synthesis of an epothilone molecules fragment (15R)-C 13 -C 21 was carried out from D-mannitol through its conversion into methyl 2,3-O-cyclohexylidene-D-glycerate followed by the cyclopropanation of the ester group with ethylmagnesium bromide in the presence of titanium(IV) isopropoxide and the transformation of the obtained cyclopropanol into the corresponding 2-substituted allyl bromide. The coupling of the latter catalyzed by copper with 2-methylthiazolyl-4-magnesium bromide, the shift of a double carbon-carbon bond in the product obtained into the position, conjugated with the thiazole ring, and the common transformation of the protected 1,2-diol function afforded the target compound in 15% yield.
A reagent combination of Ti(OiPr)4 and ethylmagnesium bromide generates low valent Ti(OiPr)3 which is readily used to transform carbonyl compounds into the corresponding pinacols. -(MATIUSHENKOV, E. A.; SOKOLOV, N. A.; KULINKOVICH*, O. G.; Synlett 2004, 1, 77-80; Dep. Org. Chem., Belarus State Univ., Minsk 220050, Belarus; Eng.) -Mais 19-032
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