Dejun Zhou

Enantioselective syntheses of (-)- and (+)-monomorine I.

A concise enantioselective total synthesis of unnatural (-)-monomorine I has been achieved starting from lactam 2 in 54% overall yield. Natural (+)-monomorine I was also synthesized.

Flexible synthetic routes to poison-frog alkaloids of the 5,8-disubstituted indolizidine-class I: synthesis of common lactam chiral building blocks and application to the synthesis of (-)-203A, (-)-205A, and (-)-219F

Background The 5,8-disubstituted indolizidines are the largest class of poison-frog alkaloids found in anuran skin, and are of considerable interest because of their inhibitory effects on the neuronal nicotinic acetylcholine receptors. Many synthetic strategies for the construction of this nucleus have been reported: however, a flexible route has not been reported to date. Results Synthesis of lactam chiral building blocks for the flexible synthesis of the title alkaloids has been achieved using a Michael-type conjugate addition reaction to a chiral cyclic enamine ester as the key step in constructing the trisubstituted piperidine ring system. To demonstrate the usefulness of these chiral building blocks, syntheses of (-)-203A, (-)-205A from 1, and (-)-219F from 2 have been achieved. Conclusion The total synthesis of (-)-203A, (-)-205A, and (-)-219F was achieved, and the absolute stereochemistry of natural 203A was determined to be 5S, 8R, 9S. In addition, the relative stereochemistry of natural 219F was determined.

SYNTHESIS, DETERMINATION OF THE ABSOLUTE STEREOCHEMISTRY, AND EVALUATIONS AT THE NICOTINIC ACETYLCHOLINE RECEPTORS OF A HYDROXYINDOLIZIDINE ALKALOID FROM THE ANT MYRMICARIA MELANOGASTER

The first chiral synthesis of new hydroxyindolizidine alkaloid (1) detected in the ant Myrmicaria melanogaster has been achieved, and its absolute stereochemistry was determined to be 3S, 5R, 8S, 9S by the present chiral synthesis.