Total Synthesis of Coralloidolides A, B, C, and E

Abstract

Mapping the matrix: Several coralloidolides, members of a Mediterranean branch of the furanocembranoid family of diterpenes, have been synthesized. The total syntheses include biomimetic transformations that often occur with high chemoselectivity, thus obviating the need for protecting‐group manipulations. The fascinating reactivity of 2,5‐diene‐1,4‐dione moieties was explored in detail.

Biosynthetic Interrelationships within Polycyclic Cembranoids Isolated from Corals: Conjecture, Biomimetic Synthesis and Reality

“…Coralloidolides B ( 140 ) and C ( 142 ), found in the Mediterranean coral Alcyonium coralloides , are examples of another family of natural products whose biosynthesis Trauner and others proposed to be from the FBC rubifolide 1 by oxidation and oxidative cleavage to the epoxy enedione 139 (coralloidolide E) followed by skeletal rearrangement. Trauner and his group later synthesised coralloidolide E ( 139 ) from rubifolide 1 which, after extensive experimentation, they were able to convert into coralloidolide B ( 140 ) on treatment with hydrated scandium triflate (Scheme ) . In other biomimetic experiments, treatment of 139 with DBU was shown to lead to coralloidolide C ( 142 ) presumably via an intramolecular aldol reaction from the enol intermediate 141 .…”

No Acid Required: 4π and 6π Electrocyclization Reactions of Dienyl Diketones for the Synthesis of Cyclopentenones and 2H-Pyrans

“…A survey of the literature reveals that cyclization of enolates of type 10 and 11 (Scheme 4 ) generates cyclopentenones with suspiciously high diastereoselectivity under basic conditions. 21 Because a canonical pentadienyl cation intermediate cannot be invoked in these reactions, one could argue that these cyclizations are intramolecular aldol reactions that occur without conservation of orbital symmetry. 22 However, the diastereoselectivity observed is difficult to rationalize unless one invokes conrotatory electrocyclization.…”

A Kinetic Dearomatization Strategy for an Expedient Biomimetic Route to the Bielschowskysin Skeleton

“…Previous efforts on furanocembranoid dearomatization were hampered by the extreme sensitivity of the dearomatized enedione 6 or enol ether 8 a products. In a model study, Pattenden and co‐workers showed that the oxidation state of the substituent on the furan was critical to tame the oxidative dearomatization with DMDO to avoid the formation of enedione 9 and favor the desired exo ‐enol ether ketal 8 a via epoxide 7 (Scheme a) .…”