Enantioselective synthesis of 2, a revised structure for (-)-clavosolide B, was accomplished by a convergent approach, where syn-selective aldol, hydroxy-directed cyclopropanation, Mitsunobu inversion, Schmidt-type glycosylation, and macrolactonization reactions were utilized as key reactions. Comparison of 1H and 13C NMR spectra and optical rotation measurement confirmed the relative and absolute stereochemistry of clavosolide B (2).

A convergent and enantioselective total synthesis of (-)-amphidinolide O (1) and P (2), 15-membered macrolides with seven chiral centers along with many functional groups, is described. The key reactions include enantioselective Brown allylation, anti- and syn-selective aldol reactions, (E)-selective olefin metathesis, conformation-controlled stereoselective epoxidation, and selective introduction of the exomethylene group. Assignments of the absolute stereochemistries of the natural (+)-amphidinolide O (ent-1) and P (ent-2) are also discussed in detail.

Enantioselective total synthesis of (-)-clavosolide A and B was reported in full including the synthesis of proposed structure of (-)-clavosoldie A (1), revised structure of (-)-clavosoldie A (5), and revised structure of (-)-clavosoldie B (6). The relative and absolute stereochemistries of the natural products were confirmed unambiguously by comparing the optical rotation values and 1 H and 13 C NMR spectra of them.

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Toward the Total Synthesis of Amphidinolide O: An Enantioselective Synthesis of C3-C8 Fragment. -Title fragment (X) is synthesized enantioselectively starting from L-(-)-malic acid (I) via 11 steps in 14 % overall yield. The diastereoselective Ireland-Claisen rearrangement of (VI) is used as a key step in order to implement the C4 and C5 chiral centers. -(HWANG, M.-H.; LEE*, D.-H.; Bull. Korean Chem.