Structural Elucidation of Cisoid and Transoid Cyclization Pathways of a Sesquiterpene

T erpenes comprise the most structurally diverseclass of natural products, playing essential eco-logical roles by mediating communication be-tween plants and insects, by providing antimicrobial de-fenses for plants, and likely acting in additional undefined capacities (as reviewedpreviously (1)). Terpe-noids originate from primary isoprenoid metabolism, wherein iterative condensation of 5-carbon isoprene units (isopentyl diphosphate and dimethylallyl diphos-phate) catalyzed by prenyltransferases produce poly-isoprenoid diphosphate substrates of varying lengths (for a review, see ref 2). Terpene synthases, in turn, of-ten referred to as cyclases given the cyclic nature of many of their products, transform the polyisoprenoid diphosphate substrates, e.g., geranyl diphosphate C10, farnesyl diphosphate C15, or geranylgeranyl diphos-phate C20, into structurally diverse mono-, sesqui-, an