Chiral γ and δ Hydroxysulfones via lipase catalyzed resolutions - synthesis of (R)(+)-4-hexanolide and (2R,5S)-2-methyl-5-hexanolide using intramolecular acylation

Acyclic 1,4-Stereocontrol via the Allylic Diazene Rearrangement: Development, Applications, and the Essential Role of Kinetic E Stereoselectivity in Tosylhydrazone Formation

We report full details of a method for 1,3-reductive transposition of α-alkoxy-α,β-unsaturated hydrazones to provide E-alkenes with high 1,4-stereocontrol between the two respective allylic stereocenters. The process couples a chelation-controlled reduction of the hydrazone with an in situ allylic strain controlled retro-ene reaction of an allyl diazene, i.e., an allylic diazene rearrangement. Such stereotriads are frequently observed motifs in natural products. We observed a fortuitous kinetic preference for the E-hydrazone geometry during the hydrazonation reaction, as only the E-isomers could undergo chelation-controlled reduction.

Enantiospecific Synthesis of Trisubstituted Butyrolactone Natural Products and Their Analogs

A general methodology for the synthesis of highly substituted butyrolactones in enantiomerically pure form has been developed. The application of this process in a highly efficient synthesis of lactone natural products blastmycinone (1), NFX-2 (2), antimycinone (3), and NFX-4 (4) and two lipid metabolites (5, 6) are described. Additionally, the total synthesis of 5-epi-blastmycinone (22), 5-epi-NFX-2 (21b), 5-epi-NFX-4 (21c), and lipid metabolite analogs (19, 20) are also described. The overall yields for the target molecules are the highest reported so far in the literature.