Addition of ester enolates to N-alkyl-2-fluoropyridinium salts: total synthesis of (±)-20-deoxycamptothecin and (+)-camptothecin

…, E Zulaica, C Juan, Y Alonso, J Bosch

Index: Bennasar, M.-Lluisa; Zulaica, Ester; Juan, Cecilia; Alonso, Yolanda; Bosch, Joan Journal of Organic Chemistry, 2002 , vol. 67, # 21 p. 7465 - 7474

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Citation Number: 49

Abstract

Several 4-substituted dihydropyridones or 2-pyridones have been prepared by nucleophilic addition of α-(methylsulfanyl) ester enolates to N-alkyl-2-fluoropyridinium salts, followed by acid hydrolysis or oxidation with concomitant hydrolysis, of the intermediate 2-fluoro-1, 4- dihydropyridine adducts, respectively. Addition of the enolate derived from isopropyl α- (methylsulfanyl) butyrate to N-(quinolylmethyl)-2-fluoropyridinium triflate 21 followed by ...