Strategies for the total synthesis of C2-C11 cyclized cembranoids.

摘要: The C2-C11 cyclized cembranoids, which include the eunicellins (also known as cladiellins), briarellins, asbestinins, and sarcodictyins, are secondary metabolites isolated from gorgonian octocorals soft corals. An unusual oxatricyclic ring system containing a hydroisobenzofuran an oxonene unit with stereogenic centers residing at C1-3, 9, 10, 14 is common to eunicellins, asbestinins. However, location of cyclohexyl methyl groups (C11 versus C12) oxidation level sixand nine-membered rings differ among three classes. Faulkner has proposed that cyclization cembranoid diterpene skeleton initiates biosynthetic pathway leads all four subclasses these molecules (Figure 1). Beginning cembrane skeleton, provides cladiellin framework. intramolecular etherification tricycle affords tetracyclic framework briarellin subclass, subsequent 1,2-suprafacial shift structure postulated deliver asbestinins class furthest evolved skeleton. presence multiple structural types in organism circumstantial evidence for Faulkner’s pathway. isolation metabolite Alcyonium molle asbestinin Briareum steckii specific examples. sarcodictyins also arise skeleton; however, systems, results fused cyclohexane oxonane place cladiellins, As result this significant variation synthetic approaches quite different than those other related subclasses. This review will cover efforts toward but not total synthesis sarcodictyins. Eunicellin was first reported member natural products, 1968 by Djerassi co-workers coral Eunicella stricta found off coast Banyuls-sur-Mer France. Since discovery, over 100 unique have been characterized, including 1980 1995. A wide range diversity displayed group marine products. role cembranoids proposed, based upon mollusk fish lethality assays, involve predation deterrence. Upon further investigation, several members demonstrated pharmacological potential. Particularly, diterpenes shown exhibit vitro cytotoxicity against various cancer cell lines, anti-inflammatory properties, antimicrobial activities, histamine acetylcholine antagonism. fascinating molecular architecture well their potential therapeutic agents, sparked much interest community past decade. variety challenging motifs investigated syntheses accomplished. Efforts subject review.