Unified Approach to ent-Eudesmane-Type Terpenoid Synthesis: Total Synthesis of Sinupol and Eutyscoparin A

Abstract

ent-Eudesmane-type terpenoids constitute a large class of natural products derived from plants, animals, and bacteria. We describe a synthetic approach to two ent-eudesmane-type terpenoids, sinupol, and eutyscoparin A, that relies on a key π-facial- and endo/exo-selective intramolecular Diels–Alder reaction to set the C-5–C-10 stereotriads. Further key transformations of trans-fused decalin include conversion to methyl ketone via a versatile thioester intermediate and appropriate functionalization toward target compounds.

Hedycaryol – Central Intermediates in Sesquiterpene Biosynthesis, Part II

“…Compounds that could biosynthetically directly arise from I5 (Scheme 19) include ent ‐α‐eudesmol ( ent ‐ 14 ) for which only one synthetic report is available. Herein, the absolute configuration was secured by MoKα X‐ray crystallography of the p ‐bromobenzoate‐epoxide of ent ‐ 14 (Flack parameter: 0.030(3)) and the optical rotation of ent ‐ 14 was found to be positive ([α] D 25 =+6.4) [183] which supports the suggested revision of the signs of optical rotation for the enantiomers of 14 [84] . The freshwater fungus Beltriana rhombica is a source of ent ‐ 15 ([α] D 29 =−37.9), [184] and (+)‐cryptomeridiol ( ent ‐ 21 ) has been reported from the cypress Chamaecyparis obtusa , [185] while ent ‐ 16 and ent ‐ 22 are unknown.…”