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

Abstract

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.

The essential oil of patchouli, Pogostemon cablin: A review

“…Subsequently its structure was revised to 17 (Table ), i.e., with the C‐7 substituent in the β‐position. The structural revision was confirmed by Srikrishna and Pardeshi, and later by synthesis …”

“…The chemical structures of most of the major SQHCs have been unambiguously confirmed by either total synthesis, like for seychellene and cycloseychellene, or hemi‐synthesis, e.g., α‐guaiene 16 and aciphyllene 17 from guaiol . Nowadays, NMR is often replacing full or hemi‐synthesis for proof of structure but errors are possible and pogostol 37 is a telling example ( vide infra ).…”

Germacrene A–A Central Intermediate in Sesquiterpene Biosynthesis

“…The synthetic compound 1-epi-aciphyllene (124)h as been prepared from guaiol (114), [314] but has not been discovered from Nature so far.I ndeed, its biosynthesis is not easily understood, as its formation through the K series (Scheme 32, Secion 5.5) of cations cannotl ead to a cis-orientation of H1 and Me14. If 124 exists at all as an atural product, two sequential 1,2-hydride migrations from J4 to J4 a and deprotonation could explain its formation (Scheme 31).…”

“…[310] It is also known as as ide product of the recombinantp atchoulol synthase from Pogostemon cablin, [290] am ulti-product terpene synthasef or which all products retain the (7R)s tereochemistry introduced in the intermediate (+ +)-1 and thus further supporting the structuralr eassignmentf or 122.M oreover,t otal syntheses from (R)-limonene by Srikrishnae tal. [318] andf rom guaiol( 114)b yH uang et al [314] were conducted. The 1 H-and 13 C-NMR data of 122 have been published.…”

“…This component was first discovered from the gurjun balsamso fs everal specieso fDipterocarpus ([a] D = + 147, CHCl 3 ). [314,319] Its absolutec onfiguration was illuminated by correlation with a-gurjunene (127)a nd guaiol (114, Scheme34B). [312] While treatment of 127 with acid gave the isomerisation products (+ +)-128 and 120 identical to natural (+ +)-g-gurjunene,t he isomerisation of 114 produced (À)-ent-128.C ompound 120 was also isolated from Persea gamblei.…”