Borohydride → 10-Deacetyltaxol

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반응 단계

In order to over come the drawbacks of the prior art processes, the applicants have developed a simple and practical process for production of taxols A, B, C; The process comprises (i) isolating the taxol analogues 7-xylosyl-10-deacetyl taxols A, B, C from the stem bark of Taxus wallichiana by an improved process developed by the applicants which involves extracting air, dried pulverized plant materials with alcohols at room temperature, evaporating the solvent to obtain a residue, stirring the resultant residue with water to a precipitate and isolating the taxol analogues 7-xylosyl-10-deacetyl taxol A, (taxol analogue A) 7-xylosyl-10-deacetyl taxol B (taxol analogue B) and 7-xylosyl-10-deacetyl taxol C (taxol analogue C) by flask chromatography over silica gel with yields 0.5% (for taxol analogue A), 0.2% (for taxol analogue B) and 0.0075% (for taxol analogue C), (ii) reacting the isolated taxol analogues A or B or C with periodates in a polar solvent at ambient temperature into dialdehyde (iii) reducing the resultant dialdehyde with borohydride in a polar solvent acetic acid mixture at 0°-40° C. into an acetal, (iv) degrading the acetal in a mixture of mineral acid and chlorinated solvent at 0°-40° C. to give the intermediate product 10-deacetyl taxol A or B or C, (v) protecting the 2', 7-hydroxyl groups of the intermediate 10-deacetyl taxol A or B or C with a suitable silane at 20°-40° C. for 20-40 hours, (vi) acetylating the free 10-hydroxyl group with an a cetylating agent at 10°-40° C. for 12-18 hours, (vii) deprotecting the silyl groups at 21, 7-positions in presence of mineral acid polar solvent mixture at 0°-10° C. to give the final product taxol A or B or C.

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