NOVEL METHOD FOR THE SYNTHESIS OF ALPHA-HALOGENONAPHTHALENE AND BETA-HALOGENONAPHTHALENE BY REGIOSELECTIVE BENZANNULATION OF ARYL(GEM-DIHALOGENOCYCLOPROPYL)METHANOLS - APPLICATION TO THE TOTAL SYNTHESIS OF THELIGNAN LACTONES, JUSTICIDIN-E AND TAIWANIN-C

Acid treatment of two types of aryl(gem-dihalogenocyclopropyl)methanol s (ADCMs) 1 and 3 gives alpha- and beta-halogenonaphthalenes in good y ields with excellent selectivity, These alternative annulations involv e two distinctive types of highly regioselective acid-induced cyclopro pane ring cleavage, wherein the preferential formation of more stable cationic intermediates determines the selectivity, The stereochemical mode of both the preparation and the annulation between diastereoisome rs of an ADCM has been checked, As a demonstration of this annulation, a total synthesis of each of the natural lignan lactones, justicidin E 19 and taiwanin C 20, has also been performed, Since these 4-arylnap hthalenes are expected to exhibit biological activity, the anti-platel et activating factor (anti-PAF) activity of justicidin E has been assa yed.