114976-68-0Relevant articles and documents
Substituent effects on the SmI2/Pd(0)-promoted carbohydrate ring-contraction of 5-alkynylpyranosides
Aurrecoechea, José M.,Gil, Jesús H.,López, Beatriz
, p. 7111 - 7121 (2007/10/03)
The effect of substituents on the reactivity and stereoselectivity of the SmI2/Pd(0)-promoted ring-contraction of 5-alkynylpyranosides has been examined using substrates substituted only at selected positions. While formation of 2-ethynylcyclopentanols takes place efficiently, an internal alkyne did not afford the expected product. The presence of peripheral alkoxy substituents leads to variable stereoselectivities that depend on the number and orientation of such groups. Thus, an isolated OBn substituent at C(3) (carbohydrate numbering) exerts a significant stereochemical control while additional substitution with the same group at C(4) either enhances or drastically reduces stereoselectivity depending on its orientation (α or β, respectively).
Towards a New Type of HMG-CoA Reductase Inhibitors: Part II: Dramatic Substituent Effects in the C-5 Epimerisation of Carbohydrate Derivatives
Bocquel, P.,Taillefumier, C.,Chapleur, Y.,Renaut, P.,Samreth, S.,Bellamy, F. D.
, p. 83 - 96 (2007/10/02)
In the course of our search for a new class of HMG-CoA reductase inhibitors, the synthesis of reaction intermediate analogues was investigated.Compound 2, having the C-5 (R) configuration of natural mevinic acids, was prepared in enantiomerically pure form starting from levoglucosan.During this synthesis, an epimerisation of the olefinic intermediate 16 was observed and was found to depend strongly both on the axial or equtorial orientation and on the nature of the C-3 substituent.Biological activity of compound 2 is reported.Keywords: HMGCoA reductase, inhibitor, carbohydrate, base catalyzed epimerisation, O-silyl protecting group.
Synthesis of a Structurally Modified Glycal. (-)-(2R,4S)-2-Methyl-2-vinyl-4-(benzyloxy)-3,4-dihydro-2H-pyran
Paquette, Leo A.,Oplinger, Jeffrey A.
, p. 2953 - 2958 (2007/10/02)
A synthetic procedure for the transformation of levoglucosan (4) to (-)-(2R,4S)-2-methyl-2-vinyl-4-(benzyloxy)-3,4-dihydro-2H-pyran (1) in 11 steps is described.The scheme relies on selective deoxygenation of the pair of α-hydroxyl groups, blocking of the β-hydroxyl, and formation of ester 16.The presence of the carboxylate group allows for stereocontrolled methylation of the enolate anion, conversion of ester to vinyl, and ultimate eliminative removal of the methoxyl substituent in methyl glycoside 25.This key transformation takes advantage of regioselective acetal cleavage by trimethylsilyl iodide and in situ dehydroiodination of the product so formed with hexamethyldisilazane.Certain unsuccessful attempts to form the α-lithio anion of 1 are also discussed.
