ALPHA-LONGIPINENE DERIVATIVES FROM SANTOLINA-VISCOSA - A CONFORMATIONAL-ANALYSIS OF THE CYCLOHEPTANE RING

The aerial pare of Santolina viscosa afforded the new longipinene derivatives, methyl longipin-9-en-15-oate [1], methyl 14-hydroxylongipin-9-en-15-oate [2], methyl 12-hydroxylongipin-9-en- 15-oate [3], methyl 14-methoxylongipin-9-en-15-oate [4], and methyl 12-methoxylongipin-9-en-15-oate [5]. Their structures were established by 2D nmr experiments and chemical correlations. The conformational analysis of the seven-membered ring was achieved through the use of nmr techniques and molecular mechanics calculations. Furthermore, a single-crystal X-ray diffraction study of the p-bromobenzoyl derivative 3 established the absolute stereochemistry of these compounds.