(1R,4S)-Calamenene. Chemical correlation with the diterpene analogues of Eremophila

Abstract

lR,4S)-(-)-Calamenene has been synthesized from dihydroxyserrulatic acid of known absolute configuration. (1R,4S)-(-)-8-Methoxycalamenene is shown to be the enantiomer of a calamenene isolated from the gorgonian Subergorgia hicksoni.

Calamenenes – aromatic bicyclic sesquiterpenes – from the Indian gorgonianSubergorgia reticulata(Ellis and Solander, 1786)

“…The structure was finally assigned as (þ)-(7R, 10S)-2-methoxy-5-acetoxy calamenene (3) from a comparison of its optical rotation, 1 H-and 13 C-NMR data ( Table 1). The 1 H-NMR values are in agreement with those reported previously for the same compound (Bunko et al, 1981;Kashman, 1979). The trans stereochemistry at C-7 and C-10 was confirmed by a comparison of the chemical shifts of C-5, C-8, C-11 and C-12 carbons of both cis and trans isomers ( Table 1).…”

“…The methyl signals at 2.37 (Ar-Me) and 3.87 (OMe) could be two of the above substitutions, while the bicyclic nature of the compound would account for the remaining two substitutions. The 1 Hand 13 C-NMR values as well as the optical rotation of 1 are in agreement with values reported previously for the same compound (Bunko et al, 1981;Kashman, 1979). The structure was further confirmed to be (þ)-(7R, 10S)-2 methoxy calamenene (1) using 2-D NMR studies such as COSY and HMBC.…”

“…Calamenenes are aromatic bicyclic sesquiterpenes of cadinane skeleton found in several terrestrial and marine organisms (Bunko, Ghisalberti, & Jefferies, 1981;Kashman, 1979;Kelman, Benayahu, & Kashman, 2000;Nakashima et al, 2002;Nishizawa, Inoue, Sastrapradja, & Hayashi, 1983;Salmoun et al, 2007). Thus, (þ)-2-hydroxy calamenene, a potent fish toxin, has been obtained from the seeds of Dysoxylum acutangulum and Dysoxylum alliaceum (Nishizawa et al, 1983).…”

“…Thus, (þ)-2-hydroxy calamenene, a potent fish toxin, has been obtained from the seeds of Dysoxylum acutangulum and Dysoxylum alliaceum (Nishizawa et al, 1983). The more polar 2,5-dioxygenated calamenenes have been isolated from gorgonians (Pseudoplexaura porosa and Subergorgia hicksoni) and soft corals (Parerythropodium fulvum fulvum and Lemnalia cervicornis) (Bunko et al, 1981;Kashman, 1979;Kelman et al, 2000). The absolute stereochemistry of the natural (þ)-calamenene and (þ)-2-hydroxy calamenene was confirmed by synthesis of both the optical isomers using ring-closing metathesis reaction followed by comparison of their 13 C-NMR spectra and optical rotation values (Nakashima et al, 2002).…”

Antifeedant Effects of Essential Oil, Extracts, and Isolated Sesquiterpenes from Pilgerodendron uviferum (D. Don) Florin Heartwood on Red Clover Borer Hylastinus obscurus (Coleoptera: Curculionidae)

“…Pure sesquiterpenes that were isolated from heartwood comprised (−)- trans -calamenene ( 1 ), cadalene ( 2 ), (−)-cubenol ( 3 ), (−)- epi -cubenol ( 4 ), (−)-torreyol ( 5 ), and (−)-15-copaenol ( 6 ) (Figure 1). The structural assignments were corroborated by the information that was published in the literature, as follows: (−)- trans -calamenene ( 1 ) [19,20,21], cadalene ( 2 ) [22], (−)-cubenol ( 3 ) and (−)- epi -cubenol ( 4 ) [16,19,23,24], (−)-torreyol ( 5 ) [16,19,25], and (−)-15-copaenol ( 6 ) [16,19]. …”