When the β-acyloxy esters (±)-10 and (±)-11 were exposed to the lipase OF-360 from Candida rugosa or immobilized lipase OF-360 in a water-saturated organic solvent, the hydrolyzed product (8aS)- was obtained in high chemical (40%) and optical (>99%ee) yields. The absolute structure of (8aS)-6 was confirmed by the fact that (8aS)-6 was converted into an authentic sample γ-keto nitrile (8aS)-17. Treatment of the diol (±)-12 with isopropenyl acetate in the presence of the lipase Godo E-4 from Pseudomonas sp. provided the unchanged (8aR)-12 (89%ee) in 42% yield.
Four newsigmatropicsequences triggered by the regiocontrolled [2,3]-Wittig rearrangement of unsymmetrical bis-allylic ethers (1) to the l,5-dien-3-ols (2) arc described, which provide unique, regiocontrolled methods for the synthesis of a wide variety of unsaturatedcarbonylcompounds possessing interesting molecular frameworks. The newly developed sequences include the [2,3]-Wittig-Claisen, the
Microwave-assisted organocatalytic cross-aldol condensation of aldehydes
作者:Dimitris Limnios、Christoforos G. Kokotos
DOI:10.1039/c3ra00114h
日期:——
An environmentally benign organocatalytic cross-aldol condensation of aldehydes under microwave irradiation in the absence of solvent is described. Using pyrrolidine as a catalyst, an efficient and sustainable atom economic method was developed for the cross-aldol condensation of various aldehydes with excellent results. Among the products, jasmine aldehyde, α-hexyl cinnamaldehyde and cyclamen aldehyde, three compounds of great industrial demand, were synthesised.
Stereoselective Directed Cationic Cascades Enabled by Molecular Anchoring in Terpene Cyclases
作者:Andreas Schneider、Philipp Jegl、Bernhard Hauer
DOI:10.1002/anie.202101228
日期:2021.6.7
cascades by exploiting the ability of anchoring dynamic substrates in the active site of terpene cyclases via designed hydrogen bonding. Thereby, it is possible to induce “directed” cyclizations in contrast to established “non-stop” cyclizations (99:1) and predestinate cascade termination at otherwise catalytically barely accessible intermediates. As a result, we are able to provide efficient access to