Guaianolides as Immunomodulators. Synthesis and Biological Activities of Dehydrocostus Lactone, Mokko Lactone, Eremanthin, and Their Derivatives

The naturally occurring guaianolides, namely mokko lactone (1), dehydrocostus lactone (2), eremanthin (3), and related guaianolides, 16, 17, 21, 22, 28−31, 33, 36, 37, and 39, have been synthesized starting from l-α-santonin in an effort to examine their structure−activity relationship as inhibitors of the killing function of cytotoxic T lymphocytes (CTL) and the induction of intercellular adhesion molecule-1 (ICAM-1). It was observed during the present study that the guaianolides possessing an α-methylene γ-lactone moiety, i.e., 2, 3, 30, 33, 37, and 39, exhibited significant inhibitory activity toward the killing function of CTL and the induction of ICAM-1.