STRUCTURE AND STEREOCHEMISTRY OF REDUCTION PRODUCTS OF ABIETIC-TYPE RESIN ACIDS

Products formed by catalytic hydrogenation of abietic, neoabietic, and levopimaric acid are correlated with those obtained by reduction with lithium in liquid ammonia. Structural and stereochemical assignments are presented for all known and several new dihydroabietic acids on the basis of hydroxylation-cleavage reactions, lactonization behavior, results on hydrogenation, and spectral data including nmr, far-uv, ORD, and CD measurements. A marked difference in the equilibrium position of the γ- and δ-lactones derived from 13α;- and 13β;-dihydroabietic acids is noted and used to define or confirm the configuration at C-13 in these acids. Newly characterized compounds include 9,5-friedoabietan-18:10-olide (15b) (13α;-dihydroabietic γ-lactone) and the following acids: 7-abieten-18-oic (7), 8(14)-abieten-18-oic (8), 13-abieten-18-oic (9), 8-abieten-18-oic (14), 13(15)-abieten-18-oic (27), and 8,13(15)-abietadien-18-oic acid (31). © 1969, American Chemical Society. All rights reserved.