Total synthesis of mycalamide A and 7-epi-mycalamide A

[formula: see text] The final stages of a total synthesis of mycalamide A are described. A key step is the aldol reaction (mismatched) of imide 4 and aldehyde 5 which provided a ca. 5:4 mixture of aldols 10a and 10b, with incorrect C(7) stereochemistry. Elaboration of the 10a-10b mixture to mycalamide A required epimerization of C(7) at the stage of beta-keto imide 11. Alternatively, Swern oxidation of the 10a-10b mixture under conditions that minimize C(7) epimerization led to 7-epi-mycalamide A selectively.     

Highly stereoselective and modular syntheses of 10-hydroxytrilobacin and three diastereomers via stereodivergent [3 + 2]-annulation reactions

A convergent synthesis of the annonaceous acetogenin, 10-hydroxytrilobacin ( 4a), was accomplished by using the [3 + 2]-annulation reaction of tetrahydrofuranyl carboxaldehyde 2a and allylsilane 3. The stereodivergency of the [3 + 2]-annulation reaction made it possible to achieve modular, highly stereoselective syntheses of three 10-hydroxytrilobacin diastereomers from the same precursors by using simple modifications of reaction conditions.     

Studies on the synthesis of apoptolidin A. 2. Synthesis of the disaccharide unit

Disaccharide 3 correspoinding to the disaccharide unit of apoptolidin A has been synthesized via the regio- and stereoselective TBS-OTf-promoted beta-glycosidation reaction of 2,6-dideoxy-2-iodo-beta-glucopyranosyl acetate (5) and p-methoxybenzyl 2,6-dideoxy-2-iodo-3-C-methyl-alpha-mannopyranoside (11).     

Stereoselective synthesis of a model C(18)-C(35) spiroketal fragment of integramycin

A highly stereoselective synthesis of a model C(18)-C(35) spiroketal unit (7) of integramycin has been accomplished via an enantioselective stannyl-crotylboration reaction and an N-iodosuccinimide-mediated spiroketalization of 19a.