Steven Mathieu

Apratoxin A Shows Novel Pancreas-Targeting Activity through the Binding of Sec 61.

Apratoxin A is a natural product with potent antiproliferative activity against many human cancer cell lines. However, we and other investigators observed that it has a narrow therapeutic window in vivo. Previous mechanistic studies have suggested its involvement in the secretory pathway as well as the process of chaperone-mediated autophagy. Still the link between the biologic activities of apratoxin A and its in vivo toxicity has remained largely unknown. A better understanding of this relationship is critically important for any further development of apratoxin A as an anticancer drug. Here, we describe a detailed pathologic analysis that revealed a specific pancreas-targeting activity of apratoxin A, such that severe pancreatic atrophy was observed in apratoxin A–treated animals. Follow-up tissue distribution studies further uncovered a unique drug distribution profile for apratoxin A, showing high drug exposure in pancreas and salivary gland. It has been shown previously that apratoxin A inhibits the protein secretory pathway by preventing cotranslational translocation. However, the molecule targeted by apratoxin A in this pathway has not been well defined. By using a 3H-labeled apratoxin A probe and specific Sec 61α/β antibodies, we identified that the Sec 61 complex is the molecular target of apratoxin A. We conclude that apratoxin A in vivo toxicity is likely caused by pancreas atrophy due to high apratoxin A exposure. Mol Cancer Ther; 15(6); 1208–16. ©2016 AACR.

Stereoselective Synthesis of the Halaven C14–C26 Fragment from D-Quinic Acid: Crystallization-Induced Diastereoselective Transformation of an α-Methyl Nitrile†

Crystallization-induced diastereoselective transformation (CIDT) of an α-methyl nitrile completes an entirely non-chromatographic synthesis of the halichondrin B C14-C26 stereochemical array. The requisite α-methyl nitrile substrate is derived from D-quinic acid through a series of substrate-controlled stereoselective reactions via a number of crystalline intermediates that benefit from a rigid polycyclic template. Therefore, all four stereogenic centers in the Halaven C14-C26 fragment were derived from the single chiral source D-quinic acid.

Prins Reaction of Homoallenyl Alcohols: Access to Substituted Pyrans in the Halichondrin Series

Prins reaction of homoallenyl alcohols with aldehyde dimethylacetals in the presence of methoxyacetic acid directly affords tetrasubstituted pyrans relevant to halichondrins with complete control of the C27 stereogenic center. Regioselective Tsuji reduction of the resultant allylic acetates stereoselectively establishes the C25 stereogenic center and C26 exocyclic olefin. Building upon these findings, we achieved concise access to the halichondrin C14-C38 and eribulin C14-C35 fragments.