A new synthesis of (-)- and (+)-esermethole (2 and 7 respectively), penultimate intermediates to (-)- and (+)-physostigmine, is described. Phase-transfer catalyzed dimethylation of 3-cyanomethyl-5-methoxyoxindole (3) and successive hydrogenation of the cyano group gave 1,3-dimethyl-3-(2-aminoethyl)-5-methoxyoxindole (5), which was efficiently resolved with optically active tartaric acids. Subsequent conversion to a carbamate and reductive cyclization performed by a standard method afforded both the enantiomers of esermethole. The enantiomeric excesses, determined by chiral HPLC analysis, were greater than 99.5%. In particular, analytical HPLC resolution of 5, previously reported as unfeasible, was achieved.
Synthesis of (-)- and (+)-esermethole via chemical resolution of 1,3-dimethyl-3-(2-aminoethyl)-5-methoxyoxindole / M. Pallavicini, E. Valoti, L. Villa, F. Lianza. - In: TETRAHEDRON-ASYMMETRY. - ISSN 0957-4166. - 5:1(1994), pp. 111-116. [10.1016/S0957-4166(00)80490-5]
Synthesis of (-)- and (+)-esermethole via chemical resolution of 1,3-dimethyl-3-(2-aminoethyl)-5-methoxyoxindole
M. PallaviciniPrimo
;E. ValotiSecondo
;
1994
Abstract
A new synthesis of (-)- and (+)-esermethole (2 and 7 respectively), penultimate intermediates to (-)- and (+)-physostigmine, is described. Phase-transfer catalyzed dimethylation of 3-cyanomethyl-5-methoxyoxindole (3) and successive hydrogenation of the cyano group gave 1,3-dimethyl-3-(2-aminoethyl)-5-methoxyoxindole (5), which was efficiently resolved with optically active tartaric acids. Subsequent conversion to a carbamate and reductive cyclization performed by a standard method afforded both the enantiomers of esermethole. The enantiomeric excesses, determined by chiral HPLC analysis, were greater than 99.5%. In particular, analytical HPLC resolution of 5, previously reported as unfeasible, was achieved.Pubblicazioni consigliate
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