Catalytic Ring Expansion of Vinyl Oxetanes: Asymmetric Synthesis of Dihydropyrans Using Chiral Counterion Catalysis
作者:Boying Guo、Gregg Schwarzwalder、Jon T. Njardarson
DOI:10.1002/anie.201201367
日期:2012.6.4
Acid Showdown! The first catalyticring expansion of vinyl oxetanes to 3,6‐dihydro‐2H‐pyrans is described. Copper(II) triflate emerged as the best catalyst for this new transformation, which has broad scope as demonstrated by the eighteen examples included. The symmetric vinyl oxetane substrate can be asymmetrically desymmetrized when using either chiral Lewis or Brønsted acids as catalysts.
Enzymatic Approach to Enantiomerically Pure 5-Alken-2,4-diols and 4-Hydroxy-5-alken-2-ones: Application to the Synthesis of Chiral Synthons
作者:Agnese Abate、Elisabetta Brenna、Alessia Costantini、Claudio Fuganti、Francesco G. Gatti、Luciana Malpezzi、Stefano Serra
DOI:10.1021/jo060581w
日期:2006.7.1
chemoenzymatic approach (lipase PS from Burkholderia cepacia). These diols were converted into useful chiralsynthons, which could be considered homologues of glyceraldehyde and glyceric acid acetonides. Applications of these synthons to the de novo synthesis of sugars and preparation of conagenin carboxylic moiety were shown. Hydroxy ketone 4 was chosen as a model system for another synthetic evolution: it