Clavularia koellikeri

An unusual combination, namely a Michael addition and a Simmons-Smith reaction, has been elaborated by the group of Alexakis [112]. Using their protocol, 3/5-as well as 3/6-annulated systems can easily be obtained, which might be useful as precursors for the total syntheses of (-)-(S,S)-clavukerin A and (+)-(R,S)-iso-clavukerin, both isolated from Clavularia koellikeri [113]. 

The dolabellane 37 (2-acetoxystolonidiol) was isolated from the soft coral Clavularia koellikeri (octocorallia order Alcyonacea family Clavulariidae) collected from a coral reef of Ishigaki Island (Yaeyama archipelago, prefec-... 

In addition to the two sinularane derivatives isolated from the marine source Clavularia inflata (see p. 114), the aromadendrane derivative (802) has also been identified in the related species Clavularia koellikeri.137 Another aromadendrane compound is the diol (803) obtained from the plant Senecio nemorensis.314 An X-ray analysis of nardosinone has confirmed its structure as (804).366 The soft coral Lemnalia africana is a rich source of sesquiterpenoids and recent investigations 383 e Trifilieff, Phytochemistry, 1980, 19, 2467. 

Tris 6>rsesquiterpenes have been isolated from a Cespitularia and two Clavularia species. 1,4-Dimethyl-2,3,3a,4,5,6-hexahydroazulene (470) was a metabolite of the former 394). The soft coral Clavularia koellikeri furnished clavukerin A (471) (395), B (472), and C (473) (396). The structure reported for clavukerin B (472) was identical with that of inflatene from Clavularia inflata (397). Inflatene (472) has shown ichthyotoxicity toward the Pacific damselfish Pomacentrus coeruleus at 10 pg/mL. A -Africanene (474), a tricyclic sesquiterpene, has been isolated from Sinularia erecta (39S) and S. polydactyla (399). 

Kobayashi, M., B.W. Son, M. Kido, Y. Kyogoku, and I. Kitagawa Clavukerin A, a New Triwor-guaiane Sesquiterpene from the Okinawan Soft Coral Clavularia koellikeri. Chem. Pharm. Bull. (Japan) 31, 2160 (1983). 

Braekman, J.C., D. Daloze, A. Dupont, B. Tursch, J.P. Declercq, G. Germain, and M. van Meerssche Chemical Studies of Marine Invertebrates-XLIII. Novel Sesquiterpenes from Clavularia inflata and Clavularia koellikeri (Coelenterata, Octocorallia, Stolonifera). Tetrahedron 37,179 (1981). 

Endo, M., M. Nakagawa, Y. Hamamoto, and T. Nakanishi Clavularins, a New Class of Cytotoxic Compounds Isolated from the Soft Coral, Clavularia koellikeri. J. Chem. Soc., Chem. Commun. 1983, 322. Erratum J. Chem. Soc., Chem. Commun. 1983, 980. 

Iwashima, M., Matsumoto, Y, Takahashi, H., and Iguchi, K. (2000b) New marine cembrane-type diterpenoids from the Okinawan soft coral Clavularia koellikeri. J. Nat. Prod., 63, 1647—1652. 

Kobayashi, M., Son, B.W., Kyogoku, Y, and Kitagawa, I. (1984c) Clavukerin C, a new trinor-guaiane sesquiterpene having a hydroperoxy function, from the Okinawan soft coral Clavularia koellikeri. Chem. Pharm. Bull, 32,1667-1670. 

Stolonilactone is a complex terpene, which may be derived by a cydoaddition [4+2]- type Diels-Alder reaction between a trisnorsesquiterpene-type diene and a cembranolide-type dienophile. This derivative was isolated from a stoloniferan of Japanese origin, Clavularia koellikeri (Igudii et al, 2004). 

---