Activating tert-butyl hydroperoxide by chelated vanadates for stereoselectively preparing sidechain-functionalized tetrahydrofurans
摘要:
tert-Butyl hydroperoxide (TBHP) stereoselectively oxidizes substituted 4-pentenols, when activated by (ethyl)[cis-(piperidine-2,6-diyl)dimethyl] vanadates. The reaction affords (tetrahydrofuran-2-yl)methanols in up to 89% yield, and in stereoselectivity ranging between moderate (cis:trans = 32:68) to excellent (>99:1). Correlating structures of 4-pentenols, differing by substitution at tetragonal and trigonal stereocenters, to configuration of products obtained from oxidative cyclization provides a reaction model explaining the origin of stereoselectivity by (i) intramolecular oxygen atom transfer to (ii) a chair-like folded alkenol, being (iii) hydrogen-bonded to one of the two aminodiolate oxygens of the chelated vanadate, having (iv) substituents in the chair-like transition structure preferentially aligned equatorially. Substituents at trigonal stereocenters improve 2,5-cis- and 2,4-trans-selectivity for oxidative 4-pentenol cyclization in case of (Z)-configuration. An (E)-substituent does not alter selectivity exerted by a terminal (Z)-substituent of similar steric size. Larger (E)-groups increase the fraction of 2,5-trans-cyclized products. The reaction model additionally implements results from vanadium-51 NMR spectroscopy and density functional theory. According to theory, the (dialkoxy)(oxo)vanadium substituent exerts in the preferred end-on conformation almost no effect on structure and bonding of the peroxide group in tert-butylperoxy vanadates. Changing conformation to a higher in energy side-on arrangement puts the vanadate-bound tert-butylperoxy group into a position to serve in a concerted reaction as combined electron acceptor and oxygen atom donor. (C) 2015 Elsevier Inc. All rights reserved.
Natural (3E,6R,7R)- and (3Z,6S,7S)-laurediols were subjected to enzymatic reaction with the partially purified bromoperoxidase from the red alga, Laurencia nipponica, in the presence of H2O2 and NaBr to afford laurencin and prelaureatin, respectively. The further reaction of these products with bromoperoxidase gave rise to the bicyclic bromo-ethers.
Enantiomeric syntheses of 6(R), 7(R) and 6(S), 7(S) trans- and cis-laurediol
作者:B Añorbe、V.S Martín、J.M Palazón、J.M Trujillo
DOI:10.1016/s0040-4039(00)85115-1
日期:1986.1
Efficient syntheses of trans-(+)-laurediol from carbohydrate precursors
作者:Rajendrakumar Reddy Gadikota、Adam I. Keller、Christopher S. Callam、Todd L. Lowary
DOI:10.1016/s0957-4166(03)00078-8
日期:2003.3
Two routes for the synthesis of the marine natural product trans-laurediol 6 are described. In the first approach 6 is obtained in ten steps and 21% overall yield from monoacetone D-glucose. The second route provides the target in eleven steps and 13% yield from D-mannose. Both routes are more efficient, both in terms of number of steps and overall yield, than previously reported syntheses. (C) 2003 Elsevier Science Ltd. All rights reserved.
FUKUZAWA, AKIO;AYE, MYA;MURAI, AKIO, CHEM. LETT.,(1990) N, C. 1579-1580
作者:FUKUZAWA, AKIO、AYE, MYA、MURAI, AKIO
DOI:——
日期:——
A short synthesis of trans-(+)-laurediol
作者:Tomás Martı́n、Vı́ctor S Martı́n
DOI:10.1016/s0040-4039(00)00190-8
日期:2000.4
A highly convergent and short synthesis of trans-(+)-laurediol is presented. The synthesis features a highly efficient construction of a cis-3-hydroxy-γ-butyrolactone through a Sharpless AD reaction of a β,γ-unsaturated ester.