Recent results in the synthesis of semiochemicals: synthesis of glycinoeclepin A
Glycinoeclepin A (11, a natural hatching stimulus for the soybean cyst nematode, was synthesized from two chiral building blocks (2 and 9) of microbial origin. Importance of chirality in the perception of semiochemicals is now well recognized (ref.1). In order to supply a significant amount of an enantiomerically pure semiochemical, biological methods such as microbial and enzymatic transformations were proved to be very useful in providing chiral building blocks (ref.2). Readily avaiable chiral building blocks like the enantiomer(s) of ethyl 3-hydroxybutanoateI methyl 3-hydroxypentanoate and 3-hydroxy-2,2dimethylcyclohexanone were extensively employed in the syntheses of various semiochemicals (ref.2). Herein we report an additional example to demonstrate the usefulness of the combined biochemical-organochemical approach in natural products synthesis. Glycinoeclepin A (1) is a degraded triterpenoid isolated from kidney bean roots as a semiochemical effective on soybean nematode (ref.3 & 4). Its unusual structure as well as its strong hatch-stimulating activity for the soybean cyst nematode made it an attractive target for synthetic chemists (ref.3 & 5 ) . Very recently Murai et al. announced the first total synthesis of 1 (ref.6). Two syntheses of simple model compounds were also reported (ref.7 & 8). We became interested in synthesizing 1 starting from two chiral building blocks of microbial origin.