86 タイロシンのアグリコン部分,タイロノライドの全合成

概要

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Tylonolide (2a), which is a 16-membered-ring aglycone of a medicinally important macrolide antibiotic, tylosin (1), has been stereospecifically synthesized by using D-glucose as a chiral source. The Michael reaction of the unsaturated ester 7, which was derived from the furanose 6 by the Wittig reaction, with the lithiated methyl methylthiomethyl sulfoxide gave stereospecifically the adducts 8a and 8b, which, finally, were converted into the aldehyde 11. The production of two adducts was found to be attributed to the asymmetry at C7, not at C6. The second Wittig reaction with the ylid 12 followed by reduction afforded a C1-C10 segment. Selective oxidation of the primary alcohol followed by esterification provided the methyl ester 14. The allylic alcohol 23, which was prepared from the branched furanose 16 through the ketose 21, was converted into the C11-C17 segment 25 by successive hydroboration, periodate oxidation, β-elimination and desilylation. Thus, the ester 14 was subjected to the aldol condensation with 25 as previously described to give the naturally derived unsaturated ketone 26, which, in turn, was converted into the pyridinethiol esters 29a and 29b. Cyclization followed by selective oxidation gave the desired 16-membered lactone, tylonolide 2a. By this completion, the absolute configuration of tylosin (1) was confirmed.
天然有機化合物討論会の論文
1981-09-10