614752-30-6Relevant academic research and scientific papers
Acetal-vinyl sulfide cyclization on sugar substrates: Effect of structure and substituent
Sasmal, Pradip K.,Maier, Martin E.
, p. 824 - 831 (2007/10/03)
A range of 2-deoxyfuranoside and -pyranoside derivatives were fashioned into derivatives that carry a vinyl or propenyl side chain. Extension of the alkene by a Suzuki cross-coupling reaction with 1-bromo-1-(phenylthio)ethene gave thioenol ethers as the cyclization substrates. The treatment of these substrates with BF3·Et2O in tert-butylmethyl ether below 0 °C induced cyclization to optically active bicyclic ethers. If the cyclizations are carried out in toluene as the solvent, the isomerization of the terminal thioenol ether to the inner thioenol ether can take place prior to the cyclization. The cyclization reactions can be impeded by steric and electronic factors. The opening of the bicyclic ethers could be illustrated with the base-induced conversion of the ketone 53 to the cyclooctenone 54.
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).
