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Novel substituted chromenopyrrolidinones were synthesized from natural amino acid derivatives through an unprecedented route involving a Knoevenagel/transesterification sequence and an allylative palladium-catalyzed cyclization reaction. The products were nature-inspired heterocycles derived from natural amino acids. The targets were synthesized with varying degrees of stereoselectivity: racemization is a known issue with amino acids, and this provided a formidable challenge to our method development. In total, six derivatives were synthesized in moderate to good yields.

A highly efficient synthetic route towards dibrominated, substituted carbazoles via an environmentally benign, regioselective bromination as the key step has been developed. Electron-rich and electron-deficient aromatic as well as aliphatic groups are well tolerated enabling access to these versatile ligand precursors in high overall yields. On larger scale the whole sequence can be performed under chromatography-free conditions.

Asymmetric synthesis of the title compound was accomplished starting from L-serine. Stannoxane-mediated lactamization provided the key intermediate in good yield.

In this paper we describe the synthesis of a diastereomer of the C(9)-C(20) dipropionate-lactone fragment of Calyculin C. A short and enantioselective synthesis of the key intermediate 2 has been developed. This intermediate will play a critical role also in the synthesis of the correct diastereomer of C(9)-C(20) dipropionate-lactone fragment of Calyculin C.

(4R)-4[(tert-Butoxycarbonyl)amino]-2-methyl-2-penten-5-olide was synthesized and hydrogenated under various catalyst/solvent systems. The best cis/trans ratio was obtained with Rh/C in diethyl ether (dr = 90 : 10). After one recrystallization, (2S,4R)-4-[(tert-butoxycarbonyl)amino]-2-methylpentan-5-olide was obtained (dr = 95 : 5, ee = 97%), which is a precursor of trans-4-methylproline.

Careful A-ring substructure analysis for taxol has been carried out and a practical synthesis to all emergent substructures, viable as A-ring building blocks, has been developed. The synthesis starts from 2-methyl-l,3-cyclohexanedione and enters via ketalized trimethylvinyltrit1ate and ketalized trimethylester to trimethylketoalcohol(s) with the hydroxyl group protected. give a clear and camprehensive survey af the feasibility af aur ap