Enantioselective synthesis of (+)-shikimic acid and (+)-5-epi-shikimic acid by asymmetric Diels-Alder reaction of (S)-α-sulfinylacrylates
摘要:
Enantiopure (S) benzyl and t-butyl 2-p-tolylsulfinylpropenoates (1 and 2) were readily prepared by Mannich condensation of (R) p-tolylsulfinylacetates (CH2O+Me2NH), followed by in situ nitrogen quaternization. These new chiral dienophiles reacted with furan at high pressures (4-13 Kbar) at rt to afford mainly a 2:1 mixture of both endo adducts (endo-B+endo-A). Enantiopure endo-4B and endo-4A were stereoselectively transformed into (+)-shikimic acid and (+)-5-epi-shikimic acid respectively, by dihydroxylation of the double bond, removal of the sulfinyl group, basic opening of the oxabicyclic skeleton and hydrolysis of the ester moiety. (C) 1997 Elsevier Science Ltd.
Enantioselective synthesis of (+)-shikimic acid and (+)-5-epi-shikimic acid by asymmetric Diels-Alder reaction of (S)-α-sulfinylacrylates
作者:Javier Adrio、Juan C. Carretero、Jose L. García Ruano、Luisa M. Martín Cabrejas
DOI:10.1016/s0957-4166(97)00151-1
日期:1997.5
Enantiopure (S) benzyl and t-butyl 2-p-tolylsulfinylpropenoates (1 and 2) were readily prepared by Mannich condensation of (R) p-tolylsulfinylacetates (CH2O+Me2NH), followed by in situ nitrogen quaternization. These new chiral dienophiles reacted with furan at high pressures (4-13 Kbar) at rt to afford mainly a 2:1 mixture of both endo adducts (endo-B+endo-A). Enantiopure endo-4B and endo-4A were stereoselectively transformed into (+)-shikimic acid and (+)-5-epi-shikimic acid respectively, by dihydroxylation of the double bond, removal of the sulfinyl group, basic opening of the oxabicyclic skeleton and hydrolysis of the ester moiety. (C) 1997 Elsevier Science Ltd.
Asymmetric Diels-Alder reaction of (S)-α-p-tolylsulfinyl α,β-unsaturated esters: the role of the sulfinyl group in asymmetric Diels-Alder reactions of vinylsulfoxides
作者:Juan C Carretero、JoséL García Ruano、Luisa M Martín Cabrejas
DOI:10.1016/s0957-4166(97)00231-0
日期:1997.7
donating electron group depending on the substitution at the double bond. In the reactions with cyclopentadiene, both reactivity and stereoselectivity raised in the presence of ZnX2 as catalysts (ZnX2>ZnBr2>ZnCl2), but TiCl4 was found to be the most efficient catalyst allowing the reactions to take place at low temperatures. With cyclopentadiene and furan, steric and electronic interactions between the