The Mechanism and Crystal Structure of 2-Methoxy-2-methyl-4-phenyl-3,4,4a, 10b-tetrahydro-2H,5H-pyrano[3,2-c]chromen-5-one. Acetal of Warfarin Acid

Özet

Abstract

Acetal of warfarin acid has been synthesized via a hemi acetal intermediate and structurally characterized by X-ray diffraction. The crystal structure shows that the title compound was formed by the hydrolysis of warfarin acid in methanol at pH 3, with space group P21/n and unit cell parameters a = 5.859 (17), b =16.745 (5), c = 16.402 (5) Å, a = 90.00; b = 94.853 (4), and g = 90.00°. Acetals are useful as protecting groups for both carbonyl compounds and alchohols.1 Acetals contribute valuable functionality to organic synthesis.2 O,O-Acetals are particularly useful as protected aldehydes and ketones, which are deprotected by mild acid hydrolysis.3 S,S-Acetals are important acyl anion equivalents (reversal of polarity), and are hydrolyzed to carbonyl compounds under oxidative conditions.4 Acid hydrolysis of other types of acetals (e.g., O,S-, N,S-, N,N-, and N,O-acetals) has also been described in the literature.5−8 Acetyals are intermediates used for the synthesis of natural products and related compounds9−11 due to the useful biological activities associated with some of their derivatives.12,13 To the best of our knowledge, there is currently only one crystal structure reported in the literature on this kind of structure