COLEON

Riiedi, P Eugster, C. H. Struktur von Coleon E, einem neuen ditepenoiden Methylenchinon aus der Coleus barbatus-Gruppe (Labiatae). Helv. Chim. Acta 1972, 55, 1994-2014. 

Riiedi, P. Neue Diterpene aus Blattdriisen von Plectranthus barbatus (Labiatae) Die absolute Konfiguration der 2-Hydropropyl-Seitenkette in Coleon E. Helv. Chim. Acta 1986, 69, 972-984. 

Arihara, S. Riiedi, P. Eugster, C. H. Diterpenoide Driisenfarbstoffe Coleone S und Taus Plectranthus caninus Roth (Labiatae), ein neues Diosphenol/traMS-A/B-6,7-Diketon-Paar aus der Abietanreihe. Helv. Chim. Acta 1977, 60, 1443-1447. 

Riiedi P. Strukturund Partialsynthese von dimerem Coleon F. Helv. Chim. Acta 1988,71, 1638-1641. 

Coleus diterpenoids. Coleus species have been a rich source of highly oxidized spiroabietanes, a number of which have been described recently. Coleons M (36 R = Ac), N (37), P (38), Q [12a-hydroxy-epimer of (38)], and coleon R, which possesses 3a-, 12a-, and 6/8-acetoxy-groups and a 7a-hydroxy-group, have been isolated39 from Plectranthus caninus whereas coleon O (36 R = H) was isolated from Coleus somaliensis. 

Lycoxanthol (24) is a hydroquinone diterpenoid which has been isolated" " from Lycopodium lucidulum. The highly oxygenated structure bears some resemblance to coleon B and to the tanshinones. 

Much effort in the diterpenoid field is concentrated on substances having biological activity. Thus the coleons, inumakilactones, and... 

Abietanes.—A number of more highly oxygenated abietanes related to the royleanones have been described recently. A new quinone, nemorone (27), has been isolated from the roots of Salvia nemorosa. Coleon C (28) and its tautomer coleon D, which possesses a trans a/b ring junction and a 6,7-diketone in place of the diosphenol on ring b, have been isolated from Coleus aquaticus. These compounds have a very characteristic u. v. spectrum. Lycoxanthol is an ether (29) which has been isolated from Lycopodium lucidulum and which possesses a very similar structure. 

The structures of these compounds were established by spectral data. UV spectra of compounds 122-125 revealed of a phenolic system conjugated with a diosphenol moiety by the addition of base, AICI3 and AICI3-HCI which showed characteristic band shifts of this cross-conjugated chromophore. These results were identical with those reported for coleon U (126), lanugons R (127) and S (128) [72]. The spectral data of compounds 122-125 were given in Tables 19 and 20. The X-ray analyses of teuvincenones A (122) and C (124) confirmed their structures. 

The leaf pigments of Coleus (Labiatae) species continue to be the source of highly oxidized diterpenoids. A group of eleven coleons and royleanones including carnosolone (36) were obtained " from C carnosus and coleon X (37) and the unusual cw-butadiene coleon Z (38) were obtained from Solenostemon... 

A number of major synthetic achievements in the diterpenoid area have been reported during the year. One of these has been the completion of the total synthesis of the insecticidal diterpenoid ryanodol (95) from the two units (93) and (94). The more highly oxidized diterpenoid phenols have attracted attention. Syntheses of the tricyclic phenol cryptojaponol, taxodione, and coleon and approaches to coleon and coleon have been reported. 

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