De Novo Enantioselective Syntheses of Galacto-Sugars and Deoxy Sugars via the Iterative Dihydroxylation of Dienoate
摘要:
[GRAPHICS]An efficient route to various sugar lactones has been developed. Key to the overall transformation is the sequential osmium-catalyzed dihydroxylation of 2,4-dienoates. The simplest (one-step/racemic) example of this reaction occurs when the dihydroxylation is performed with aqueous NMO in MeOH. When the first dihydroxylation is performed using the AD-mix procedure, an enantioselective variant results. When a matched AD-mix procedure is used for the second dihydroxylation, an exceedingly diastereo- and enantioselective synthesis of galacto-1,4-lactone results.
An asymmetric, catalytic, and direct self-aldol reaction of acetaldehyde was catalyzed by diarylprolinol in NMP, affording the trimer acetal, which was generated by the reaction of the self-aldol product with another acetaldehyde molecule in a moderate yield with good enantioselectivity. Acetal is the synthetic equivalent of the self-aldol product, which can be converted into other synthetically useful
An Enantioselective Synthesis of Cryptocarya Diacetate
作者:Thomas J. Hunter、George A. O'Doherty
DOI:10.1021/ol016399t
日期:2001.8.1
enantioselective synthesis of cryptocarya diacetate has been achieved in 10 steps from ethyl sorbate. The route relies upon an enantio- and regioselective Sharpless dihydroxylation and a palladium-catalyzed reduction to form a delta-hydroxy-1-enoate, which was subsequently converted into a benzylidene-protected 3,5-dihydroxy carboxylic ester. This ester was converted into cryptocarya diacetate in 14% overall
De novo asymmetric syntheses of C-4-substituted sugars via an iterative dihydroxylation strategy
作者:Md. Moinuddin Ahmed、George A. O’Doherty
DOI:10.1016/j.carres.2006.03.024
日期:2006.7
highly efficient route to various C-4 substitutedsugar lactones has been developed. The key to the overall transformation is the sequential osmium-catalyzed dihydroxylation reaction of substituted 2,4-dienoates and an allylic substitution at the C-4 position. When the Sharpless AD-mix procedure is used in a matched sense for the second dihydroxylation reaction, it results in an exceedingly diastereo-
An Enantioselective Synthesis of Benzylidene-Protected <i>syn</i>-3,5-Dihydroxy Carboxylate Esters via Osmium, Palladium, and Base Catalysis
作者:Thomas J. Hunter、George A. O'Doherty
DOI:10.1021/ol0156188
日期:2001.4.1
[GRAPHICS]The enantioselective syntheses of several protected syn-3,5-dihydroxy carboxylic esters have been achieved from the corresponding achiral 1,3-dieneoates, The route relies upon an enantio- and regioselective Sharpless dihydroxylation and a palladium-catalyzed reduction to form delta -hydroxy-1-enoates, The resulting delta -hydroxy-1-enoates are subsequently converted into benzylidene-protected 3,5-dihydroxy carboxylic esters in one step, The benzylidene-protected 3,5-dihydroxy carboxylic esters are produced in good overall yields (25% to 51%) and high enantiomeric excesses (80% to >95%).
A Method for Constructing the C18−C28 Dispiroacetal Moiety of Altohyrtin A