Enzyme catalyzed addition of hydrocyanic acid to substituted pivalaldehydes — A novel synthesis of (R)-pantolactone
作者:Franz Effenberger、Joachim Eichhorn、Jürgen Roos
DOI:10.1016/0957-4166(94)00384-n
日期:1995.1
(R)-Cyanohydrins (R)2b-h are obtained in good optical yields by (R)-oxynitrilase catalyzed enantioselective addition of HCN to beta-substituted pivalaldehydes 1b-h. Under optimized reaction conditions with highly purified (R)-oxynitrilase, hydroxypivalaldehyde (1a) is converted to (R)-2a in satisfactory chemical and optical yields. By acid-catalyzed hydrolysis the cyanohydrins (R)-2a-h cyclize directly to give crude (R)-pantolactone (R)-3 with ee-values of 56-95% which, after recrystallization, go up to greater than or equal to 98%ee in all cases.
Distinct Chemoselectivities in the Platinum-Catalyzed 1,2-Carboalkoxylations of 5-Alkoxypent-1-yn-3-ol Derivatives
作者:Chun-Ming Ting、Chiou-Dong Wang、Rupsha Chaudhuri、Rai-Shung Liu
DOI:10.1021/ol2002144
日期:2011.4.1
derivatives 5 produces 2,6-dioxabicyclo[3.1.0]hexanes 6; the mechanism is postulated to involve a hydroxyl-triggered [3.3]-sigmatropic allylrearrangement. As the same catalysis is extensible to their tertiary alcohol analogues 7, distinct dihydrofuranyl alcohols 8 were obtained through a [3.3]-allyl rearrangement that is not assisted by the hydroxyl group.