Cerheptaric Acid, A new lactone-forming acid isolated from cereus peruvianus (L.) mill

A systematic study of the acid-catalyzed fusion-reaction is reported. The influence of the nature and stereochemistry of the d-aldopentofuranose and the effect of the substituent at C-2 have been investigated by using indazole as a model heterocycle. The results obtained show that the nature and stereochemistry of the starting, per-O-acetylated d-aldopentofuranose have no significant effect upon the product distribution of the acid-catalyzed fusion-reaction. The use of a sugar lacking a participating group at C-2 showed, however, that the absence of participation increases the ratio of cis-1′,2′-nucleosides, and the mechanism involved is discussed. In all cases, the results indicated that the distribution of the products is determined by their relative, thermodynamic stabilities.