13-epi Manoyl oxide

Ent -3p-hydroxy 13-epi-manoyl oxide (7) (ribenol), Fig. (7), has been used as starting material for a biotransformation process by Curvularia lunata. The in vitro micropropagation of the Sideritis foe tens species has been described and several entananoyl oxide derivatives, as well as other labdanes, have been isolated from micropropagated plants. Recently, biotransformation by Curvularia lunata of some en/-l 3-e/n-manoyl oxides functionalized at C-3 or C-3 and C-12 produced derivatives, which inhibited the growth of the pathogenic protozoa, Leishmania donovani [130],... 

Dill6 en(-13-ep/-Manoyl oxide Dili enl -16-Hydroxy-3-oxo-1 i-epi -manoyl oxide... 

It has been shown that the reaction field approach may be useful in the assignment of peaks in the n.m.r. spectra of polar molecules. The positions of the C-10, C-8 and C-13 methyl resonances of epi-manoyl oxide (4) in various solvents are given in Table II together with... 

The aerial parts of Conyza steudellii (Asteraceae) have given new labdane xylosides, while from the leaves of Conyza trihecatactis, a xylopyranoside of 13-epi-sclareol has been isolated among other labdanes [104,105]. Havardic acids A-F (as methyl esters), have been isolated from another genus of the Asteraceae family, i.e Grindelia havardii [106]. 11-oxo-manoyl oxide derivatives and coleosol, which is also a manoyl oxide derivative, have been obtained from Coleus forskohlii (Labiateae) [107,108] while from another plant of the Labiatae family, Roylea calycina a tumor inhibitory compound, namely precalyone, as well as calyone have been isolated [109]. 

The study of manoyl oxide derivatives i.e. 7 and 8 in, Fig (7), (i.e ent-hydroxy and en/-acetoxy-3(3-manoyl oxides) isolated from Cistus creticus, by GC-MS resulted in only one peak indicative of the purity of the products [33]. From the H-NMR data it is clear that the 13-epi isomer was present in both derivatives [58,139]. The chromatographic data of the compounds 7 and 8 were recently published [33,63]. Hence, investigations have proven that, apart from the 13-epi isomer, there are more isomers with varying intensities, which correspond to isomers that arise from the different configuration of C-8 chiral center [33]. This isomer showing a different configuration at C-8 has been isolated from the volatile leaf oil of Alaska (yellow) cedar and its structure has been confirmed using spectroscopic methods as well as chemical reactions [150],... 

Apart from forskolin, a number of other manoyl oxides have been shown to interact with the AC enzyme system. Biotransformation of certain ent- 3-epi-manoy oxides by Curvularia lunata resulted in compounds functionalized in C-3 or in C-3 and C-12, which exhibited an AC stimulatory effect, although milder than that of forskolin (about 30 times less) [173]. The same activity was also ascribed to some synthetic derivatives of en/-8a-hydroxy-13 (16), 14 dien-18-oic acid methyl ester [178,179], The biotransformation of ent-manoyl oxide-16-hydroxy 18-oic acid methyl ester with Rhizopus nigricans, however, resulted in carbomanoyl oxide which showed a selective inhibitory action on the activity of adenylate cyclase depending on the material initially used to stimulate the enzyme. This manoyl oxide inhibited the activity of the enzyme previously stimulated by forskolin but not by glucagon. A manoyl oxide ent-3fi, 6/ -dihydroxy-13-e/ z-manoyl oxide) which also inhibited the activity of AC, was produced from the biotransformation of... 

This structure is apparently identical to a compound from Coespeletia lutescens named 3p-Hydroxy-13-epi-ent-manoyl oxide for which the published structure did not indicate a 13-epi-orientation.]... 

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