Baburaj Baskar

Gold(I)-Catalyzed Divergence in the Reactivity of 3-Silyloxy 1,6-Enynes: Pinacol-Terminated vs Claisen-Terminated Cyclization Cascades

On activation with catalytic amounts of gold(I) complexes, 3-silyloxy 1,6-enynes can react through two alternative pathways. In one, a cascade reaction consisting of carbocyclization and subsequent pinacol rearrangement takes place. In the second pathway, a heterocyclization is followed by a Claisen rearrangement. The reaction outcome differs depending on the substitution pattern of the 3-silyloxy 1,6-enynes and, more importantly, the electronic properties of the gold-bound phosphane ligand.

Biocatalytic deracemisation of α-hydroxy esters: high yield preparation of (S)-ethyl 2-hydroxy-4-phenylbutanoate from the racemate

Abstract Biocatalytic deracemisaton of the racemic ethyl ester of 2-hydroxy-4-phenylbutanoic acid gives the ( S )-enantiomer exclusively in >99% e.e. and 85–90% yield. Ethyl and methyl esters of mandelic acid and the methyl ester of 2-hydroxy-4-phenylbutanoic acid also gave the ( S )-enantiomer exclusively. Whole cells of Candida parapsilosis (ATCC 7330) were used to effect this biotansformation.

Natural product biosynthesis inspired concise and stereoselective synthesis of benzopyrones and related scaffolds.

A natural product biosynthesis-inspired strategy to explore biologically relevant chemical space is presented. A phosphine-catalyzed cascade and stereoselective annulation provides a common tricyclic benzopyrone intermediate that was efficiently transformed into diverse and related naturally occurring scaffolds.

Stereoselective Cascade Double-Annulations Provide Diversely Ring-Fused Tetracyclic Benzopyrones

A cascade double-annulation strategy employing diverse pairs of zwitterions with 3-formylchromones is presented that provides stereoselective access to complex tetracyclic benzopyrones. Different zwitterions incorporated different rings that include aza-, oxa-, and carbocycles fused to a common benzopyrone scaffold and in the process created three contiguous chiral centers including an all-carbon-quaternary center with high efficiency and excellent stereoselectivity.