A Retro-Claisen Approach to Dolabriferol

Truncated Actin-Targeting Macrolide Derivative Blocks Cancer Cell Motility and Invasion of Extracellular Matrix

Cancer metastasis is a complex process involving highly motile tumor cells that breach tissue barriers, enter the bloodstream and lymphatic system, and disseminate throughout the body as circulating tumor cells. The primary cellular mechanism contributing to these critical events is the reorganization of the actin cytoskeleton. Mycalolide B (MycB) is an actin-targeting marine macrolide that can suppress proliferation, migration, and invasion of breast and ovarian cancer cells at low nanomolar doses. Through structure-activity relationship studies focused on the actin-binding tail region (C24-C35) of MycB, we identified a potent truncated derivative that inhibits polymerization of G-actin and severs F-actin by binding to actin's barbed end cleft. Biological analyses of this miniature MycB derivative demonstrate that it causes a rapid collapse of the actin cytoskeleton in ovarian cancer cells and impairs cancer cell motility and invasion of the extracellular matrix (ECM) by inhibiting invadopodia-mediated ECM degradation. These studies provide essential proof-of-principle for developing actin-targeting therapeutic agents to block cancer metastasis and establish a synthetically tractable barbed end-binding pharmacophore that can be further improved by adding targeting groups for precision drug design.

Ring Opening of Donor-Acceptor Cyclopropanes with Acyclic 1,3-Diketones for the Synthesis of 1,6-Dicarbonyl Compounds

1,6-Dicarbonyl compounds, representing the formal addition products of the α-position of acetophenone derivatives to donor-acceptor cyclopropanes, were synthesized in two steps via first ring opening of donor-acceptor cyclopropanes with acyclic 1,3-diketones followed by DBU catalyzed retro-Claisen-type C-C bond cleavage reactions. In the first step, acyclic 1,3-diketones selectively worked as C-nucleophiles to add to donor-acceptor cyclopropanes. In the second step, the alkyl ketone part of the ring-opening products resulting from unsymmetrical 1,3-diketones was selectively cleaved in the presence of DBU in methanol.

Total Synthesis and Absolute Configuration of Simpotentin, a Potentiator of Amphotericin B Activity

The total synthesis of simpotentin (1), a new potentiator of amphotericin B activity against Candida albicans, was achieved. Our research results enabled the access of all stereoisomers of 1 and the elucidation of the unknown absolute configuration of 1. Furthermore, one of the stereoisomers is a better amphotericin B potentiator than 1 and is an excellent lead compound for the development of a novel amphotericin B potentiator.

Dolabriferols B and C, non-contiguous polypropionate esters from the tropical sea hare Dolabrifera dolabrifera

The Caribbean mollusc Dolabrifera dolabrifera from Puerto Rico contains two new propionate-derived metabolites, dolabriferol B and C (2 and 3), in addition to the known compound dolabriferol (1). The structures of dolabriferol B (2) and C (3) were established by comparison of their spectral data with those of 1, and the absolute configuration of 2 was determined from chemical degradation studies. The structure of dolabriferol C (3) was confirmed by X-ray analysis.

Total synthesis of hoiamide C

Hoiamide C was synthesized in 16 steps with an overall yield of 1.8% starting from homoallylic alcohol 18, unambiguously confirming its structure.

Enantioselective Synthesis of the Alcohol Moiety of Dolabriferol

Dolabriferol is a marine polypropionate characterized by an unusual noncontiguous carbon backbone. The two polypropionate subunits are linked by an ester function. The protected alcohol moiety of dolabriferol was synthesized via the enzymatic desymmetrization of meso-(anti-anti)-2,4-dimethyl-1,3,5-pentanetriol.