Microbial transformation of sesquiterpenoids—I

Hedycaryol – Central Intermediates in Sesquiterpene Biosynthesis, Part II

The known sesquiterpenes that arise biosynthetically from hedycaryol are summarised. Reasonings for the assignments of their absolute configurations are discussed. The analysis provided here suggests that reprotonations at the C1=C10 double bond of hedycaryol are directed toward C1 and generally lead to 6–6 bicyclic compounds, while reprotonations at the C4=C5 double bond occur at C4 and result in 5–7 bicyclic compounds. Read more in the Review by H. Xu and J. S. Dickschat (DOI: 10.1002/chem.202200405).

Revisiting the Chemistry of Guaiacwood Oil: Identification and Formation Pathways of 5,11- and 10,11-Epoxyguaianes

Guaiacwood oil from Bulnesia sarmientoi Lorentz ex. Griseb is a common natural ingredient of the perfume industry used in both domestic and luxury fragrances for its highly appreciated woody-rosy odor, as well as its excellent fixative properties. Despite its long and traditional use as a perfume ingredient, guaiacwood oil has not been extensively studied. Thus, the chemical characterization of its constituents by using a full array of GC-hyphenated techniques (GC-MS, GC × GC-MS, and pc-GC) combined with conventional chemical fractionation was undertaken. In the course of this work, 15 new sesquiterpenoids mostly belonging to the 5,11- and 10,11-epoxyguaiane families were identified. Each isolated compound was fully characterized by NMR and MS. Collectively, the specific chemical relationships observed between sesquiterpene oxides and alcohols permitted the formulation of probable formation pathways regarding their presence as natural constituents of guaiacwood extracts.

Synthesis of guaia-4(5)-en-11-ol, guaia-5(6)-en-11-ol, aciphyllene, 1-epi-melicodenones C and E, and other guaiane-type sesquiterpenoids via the diastereoselective epoxidation of guaiol

The diastereomeric ratio of epoxidation of the internally bridged carbon-carbon double bond of guaiol (1a) is strongly influenced by the combined effects of the types of remote protecting groups on the hydroxyisopropyl side chain, choice of solvent, and epoxidizing reagent. This observation has allowed us to devise concise stereoselective syntheses of a range of guaiane-type sesquiterpenoids via an epoxidation, ring-opening/elimination, and functionality manipulation sequence. Natural products guaia-4(5)-en-11-ol (2a), guaia-5(6)-en-11-ol (3), and aciphyllene (4a) and epimers of the recently isolated natural products, 1-epi-guaia-4(5)-en-11-ol (2b), 1-epi-aciphyllene (4b), and 1-epi-melicodenones C (5a) and E (6a), were synthesized in good yields in relatively few steps.