Aromatic Ring Derivatives, Actiphenol and Actiketal

The antimicrobial activity of cycloheximide derivatives with an unsaturated double bond in the cyclohexanone ring decreased as inactone (31) [23] and actiphenol (32) [24]. On the other hand, actiketal (RK-441S, 33), a unique benzofuran-type derivative, was isolated from a culture extract of Strepto-myces pulveraceus subsp. epiderstagenes [25]. This compound showed inhibitory activities towards Con A-induced blast formation in spleen cells (100% at 20 nM), and towards the incorporation of [3H]thymidine into epidermal growth factor-stimulated Balb/MK cells (IC5o 14.5 ^M). Kiyota-Oritani's group first tried a semi-synthesis from 32 (Scheme 5) [26], i.e.,

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