Photocyclodimers from Z-ligustilide.: Experimental results and FMO analysis

The irradiation of the natural phthalide Z-ligustilide (1) gave the natural dimeric phthalide riligustilide (5), and three novel dimeric phthalides 7, 8 and 9. The chemo- and regio-selectivity involved in the formation of the photocyclodimers were analyzed by use of frontier molecular orbital methods and the preference in the formation of 7 was supported by the theoretical analysis. (c) 2005 Elsevier Ltd. All rights reserved.