Coupling of activated esters to gramines in the presence of ethyl propiolate under mild conditions.

The coupling of activated esters to gramine derivatives is described using ethyl propiolate. A series of substrates have been prepared using these mild conditions to provide a scope and limitations for this methodology.

Concise, asymmetric, stereocontrolled total synthesis of stephacidins A, B and notoamide B.

Concise asymmetric total syntheses of the fungal metabolites (-)-stephacidin A, (+)-stephacidin B, and (+)-notoamide B are described. Key features of these total syntheses include (1) a facile synthesis of (R)-allyl proline methyl ester, (2) a revised route toward the pyranoindole ring system, (3) a novel cross-metathesis strategy for the introduction of important functional groups, and (4) an SN2' cyclization to form the [2.2.

Synthetic studies on perophoramidine and the communesins: construction of the vicinal quaternary stereocenters.

An efficient synthetic strategy for installation of the two vicinal quaternary carbon centers of the communesins is reported. Key steps include the O-allylation/Claisen rearrangement of spirolactone systems, which are formed by tandem intramolecular Heck cyclization/carbonylation. Substituent and solvent effects on the stereochemical outcome of the Claisen rearrangements have been examined.

An approach to the total synthesis of the marine ascidian metabolite perophoramidine via a halogen-selective tandem Heck/carbonylation strategy.

A halogen-selective tandem intramolecular Heck/carbonylation reaction has been developed for the construction of the C,E,F-ring system and the C20 quaternary center found in perophoramidine (1). This process can be effected in good yields in the presence of both the chlorine and bromine atoms found in the natural product. In addition, it is possible to introduce the quaternary center at C4 in a stereoselective manner by a lactone enolate alkylation, using NaH and allyl bromide.