A new bis-annelation method. Application to steroid synthesis

Concise Total Synthesis of Peyssonnoside A

Peyssonnoside A is a marine-derived sulfated diterpenoid glucoside with a unique 5/6/3/6 tetracyclic skeleton with a highly substituted cyclopropane ring deeply embedded into the structure. Herein, we report the first total synthesis of this natural product in a concise, efficient, scalable, and highly diastereoselective fashion. The aglucone peyssonnosol was synthesized in 21% overall yield after 15 steps, featuring a Simmons-Smith cyclopropanation and Mukaiyama hydration, fully controlled by the spatial structure of the substrates.

Formal synthesis of (-)-englerin A and cytotoxicity studies of truncated englerins

An efficient formal synthesis of (-)-englerin A (1) is reported. The target molecule is a recently isolated guaiane sesquiterpene that possesses highly potent and selective activity against renal cancer cell-lines. Our enantioselective strategy involved the construction of the BC ring system of compound 1 through a Rh(II)-catalyzed [4+3] cycloaddition reaction followed by subsequent attachment of the A ring through an intramolecular aldol condensation reaction. As such, this strategy allows the synthesis of truncated englerins. Evaluation of these analogues with the A498 renal cancer cell-line suggested that the A ring of englerin is crucial to its antiproliferative activity. Moreover, evaluation of these analogues led to the identification of potent growth-inhibitors of CEM cells with GI(50) values in the range 1-3 μM.

Enantioselective formal synthesis of (-)-englerin A via a Rh-catalyzed [4 + 3] cycloaddition reaction

An enantioselective formal synthesis of (-)-englerin A (1) is reported. Key to the strategy is a Rh-catalyzed [4 + 3] cycloaddition reaction between furan 10 and diazo ester 11 that, following an intramolecular aldol condensation, produces the tricyclic scaffold of englerin. This strategy also provides a rapid, efficient, and stereoselective access to the biologically significant core motif of the guaiane sesquiterpenes.

Novel Routes to Chiral 2-Alkoxy-5-/6- methoxycarbonylmethylidenepyrrolidines/-piperidines

We report the results of a study aimed at the diastereoselective synthesis of chiral 2-alkoxy-5-/6-methoxycarbonylmethylidenepyrrolidines/-piperidines by condensation of chiral amines onto omega-oxo alkynoates and omega-oxo beta-keto esters.