Philip J. Kocienski

An approach to the synthesis of (–)-lipstatin by Wittig reaction and Lewis acid-promoted [2 + 2] cycloaddition

The β-lactone moiety of (–)-lipstatin 1, a potent inhibitor of pancreatic lipase, is prepared via a Lewis acid-promoted [2 + 2] cycloaddition between hexyltrimethylsilyl ketene 3 and the (Z,Z)-dienic aldehyde 4, obtained from hexanal by two stereoselective Wittig reactions.

α-Heteroalkenyl Metallate Rearrangements in Organic Synthesis

The scope, stereochemistry and mechanism of 1,2-metallate rearrangements of borates and cuprates derived from 5-lithio-2,3-dihydrofuran and 6-lithio-2,4-dihydro-2H-pyrans is compared with borates and cuprates derived from α-metallated enol carbamates. Depending on the metallate complex and the substrate, 1,2-alkyl shifts can take place by several mechanisms.