A High-Throughput Screening Method for the Directed Evolution of Hydroxynitrile Lyase towards Cyanohydrin Synthesis.

Chiral cyanohydrins are useful intermediates in the pharmaceutical and agricultural industries. In nature, hydroxynitrile lyases (HNLs) are a kind of elegant tool for enantioselective hydrocyanation of carbonyl compounds. However, currently available methods for demonstrating hydrocyanation are still stalled at precise, but low-throughput, GC or HPLC analyses. Herein, we report a chromogenic high-throughput screening (HTS) method that is feasible for the cyanohydrin synthesis reaction. This method was highly anti-interference and sensitive, and could be used to directly profile the substrate scope of HNLs either in cell-free extract or fermentation clear broth. This HTS method was also validated by generating new variants of PcHNL5 that presented higher catalytic efficiency and stronger acidic tolerance in variant libraries.

An Enantioconvergent and Concise Synthesis of Lasonolide†A.

Efficient access to medicinally significant natural products is an essential basis for the development of pharmaceuticals. The limited availability of marine natural products impedes broad biological evaluation. Despite several elegant syntheses of (-)-lasonolide A having been reported, a practical synthesis of this potent anticancer polyketide remains elusive. Based on the application of borane as a traceless protecting group and the development of an unprecedented bissulfone reagent for Julia olefination, (-)-lasonolide A was assembled in an enantioconvergent manner through the application of stereoselective hydroboration, allylation, and oxidation. This concise route may provide a realistic solution for accessing derivatives and analogues.

Stereodivergent Synthesis of Functionalized Tetrahydropyrans Accelerated by Mechanism-Based Allylboration and Bioinspired Oxa-Michael Cyclization.

A stereodivergent strategy enabled by bioinspired oxa-Michael cyclization was developed for the synthesis of functionalized tetrahydropyrans on the basis of the inherent symmetry in 1,3-diols, the symmetries of which were tunable by stereoselective hydroboration of an allene with a variety of alkylborane reagents and subsequent allylation of an aldehyde. The mechanism-based utilization of monoalkyl borane in the hydroboration and allylation cascade is unprecedented.

All-in-One Synthesis of 3,6-Dideoxysugars: An Olefin Metathesis-Isomerization Approach.

A collective synthesis of 3,6-dideoxysugars, including seven naturally known congeners, has been reported using commercially available methyl lactates in five steps. The essential tandem process involving the olefin cross-metathesis and isomerization steps was enabled by the dual function of Grubbs-II catalyst, affording the products in good yields and providing concise and practical access to a class of biologically important deoxysugars.