Synthesis Of C13 Research Articles

Studies Toward the Stereoselective Synthesis of C13 to C21 Fragment of the Brasilinolides Family of Immunosuppressive Macrolides

The work describes our attempts to synthesize the C13 to C21 fragment of brasilinolides, a 32-membered macrolide class of molecule. The C13 to C21 segment encompasses six asymmetric centers and a pyran ketal moiety. The synthesis starts from L-malic acid, and the salient features of our asymmetric synthesis are opening of epoxide, assymmetric dihydroxylation for the creation of vic-diol, and Barbier allylation.

Stereoselective Synthesis of C13–C28 Fragment of Marinomycin A

Synthesis of the C13–C28 fragment of marinomycin A, consisting of all the five stereocenters, was achieved by asymmetric synthesis, starting from l -malic acid. The simple convergent approach utilized cross metathesis of two key olefinic fragments for the introduction of the C20–C21 double bond. Two of the five stereocenters, C19 and C27, were realized from l -malic acid, while, C17 and C23 are introduced by Sharpless asymmetric epoxidation and C25 by a selective allylation reaction.

Synthesis of C13−C25 Fragment of 24-Demethylbafilomycin C1 via Diastereoselective Aldol Reactions of a Ketone Boron Enolate as the Key Step

An efficient synthesis of the C13-C25 fragment is described for 24-demethylbafilomycin C1, a new member of the plecomacrolide family isolated from fermentation broth of Streptomyces sp. CS which is a commensal microbe of Maytenus hookeri. The targeted C13-C25 fragment possesses five oxygenated and three methyl-substituted stereogenic centers. It is obtained through formation of the C17-C18 syn aldol by using an ethyl ketone boron enolate with diastereomeric ratios of 95:5 and 83:17, respectively, for the chiral aldehydes substituted with acetoxy and methoxyacetoxy groups at C15. The results confirm the observation that the stereochemistry at C22 of the ketone is determinant to the diastereoselectivity of the aldol reaction. The synthesized C13-C25 fragment having a methoxyacetoxy group at C15 is considered as a useful precursor for construction of the 16-membered ring lactone of 24-demethylbafilomycin C1 through an aldol condensation of the methoxyacetate followed by formation of the C12-C13 double bond via a diene-ene RCM reaction.