Phyllocladene

In addition to the above-described terpenes proper, there are a few other hydrocarbons which may be conveniently dealt with here. These are salvene, the so-called olefinic terpenes, myrcene and ocimene, the terpene homologues, cantharene, santene, and a hydrocarbon of the formula CjjHjg found in sandalwood oil, and the diterpene phyllocladene. 

Baker and Smith have isolated from the essential oil of the leaves of Phyllodadus Rhomboidalis a diterpene, which they have named phyllocladene It has the formula C2UH32, and melts at 95°. It is dextro-rotatory, its specific rotation being -t- 16-06°. 

Kaur-15-ene 122, kaur-16-ene 123 and phyllocladene 124 (Structure 4.38) are encountered in essential oils. 

A total synthesis of ( )-royleanone from 5,7,8-trimethoxy-l-tetralone (123) has been described.129 The tetralone was converted into the tricyclic ketone (124), which was in turn converted into 11,12,14-trimethoxypodocarpatriene (125). Demethyla-tion and oxidation afforded the quinone (126 R = H) which was alkylated to give royleanone (126 R = Pr ). Synthetic studies in the resin acid series have led130 to the preparation of the dicarboxylic acid (127) with a cis a/b ring junction. The preparation of some tetracyclic ketones as intermediates for gibberellin synthesis has been described.131 132 The key reaction involves photolysis of a diazoketone (128) to afford the tetracyclic system (129). In a synthesis of phyllocladene from abietic acid... 

The Chemistry of the Tetracyclic Diterpenoids.—The reaction of cnt-kaur-16-ene with thallium(lli) nitrate affords cnt-kaur-16-en-15j8-ol nitrate which undergoes a ready [3,3] sigmatropic rearrangement to cnt-kaur-15-en-17-ol nitrate. The reactions of phyllocladene and of labda-8(17)-en-13-ol with sodium azide and iodine chloride have been examined. ° The synthesis of 13-hydroxylated cnt-kaur-16-ene derivatives such as steviol using an acyloin-like cyclization of keto-esters has been developed. A detailed analysis was made of the products arising from the use of sodium in liquid ammonia in this reaction. 

However, reductions of aromatic ketones over Rh or Ru in appropriate solvent and under elevated pressure afford saturated carbinols with maintenance of benzyl oxygen, as in the synthesis of natural products such as d-phyllocladene ... 

The Kaurane-Phyllocladane Series.— There have been several chemotaxonomic studies on the distribution of diterpene hydrocarbons amongst the Podocar-paceae, Sciadopityaceae, and Taxodiaceae. A more detailed study of eighty-four specimens of Cryptomeria japonica reveals an infra-species variation in hydrocarbon production. Thus although sixty-six trees produced (—)-kaurene, nine produced phyllocladene of the opposite stereochemical series. Indeed, even trees from the same seed source were not uniform in their hydrocarbon production. This paper also records a warning of the facile isomerisation of kaurene and phyllocladene into their A -isomers. 

Djerassi C., Cais M. and Mitscher L.A. (1959) Terpenoids. XXXVII. The structure of the pentacyclic diterpene cafestol. On the absolute configuration of diterpenes and alkaloids of the phyllocladene group. J. Am. Chem Soc. 81, 2386 98. 

The metabolism of ent-kaur-16-ene by Gibberella fujikuroi in the presence of the plant-growth retardant (78) follows the normal pattern. However, kaur-16-ene, phyllocladene (13/3-kaur-16-ene), with the steroid-like a/b fusion, and ent-kaur-15-ene were not metabolized. The transformation by Gibberella fujikuroi of 2- and 3-hydroxylated kaurenoids to a range of hydroxylated... 

N.m.r. solvent-shift studies indicatedthat the (5-lactones obtained by opening ring D of phyllocladene exist in the chair form. Phyllocladene is an abundant... 

In 1961, two experiments which provided the basis for deducing the skeleton of enmein were carried out by Kanatomo (75, 16). In the first he obtained l-ethyl-4(3,3-dimethylcyclohexyl)-benzene (II) whose structure was proved by synthesis (75). In the second he isolated retene (III) by selenium dehydrogenation of the material obtained by LiAlH4 reduction of enmein (16). Thus enmein was proved to be a diterpene and a phyllocladene (IV) skeleton was proposed for it (16). Kubota and coworkers (77) deduced the presence of a hemiacetal ring (V) and partial structure (VI), with the lactone function part of a six-membered ring, on the basis of chemical evidence and spectral data of various derivatives, and advanced four formulas including (VII) as possible structures for enmein. 

Since e -16-kaurene (116) has been converted to phyllocladene, atisirene, and neoatisirene, the foregoing conversion also implies a formal chemical conversion of enmein to these diterpenoid hydrocarbons. 

Sclareol (29) and manool (30) (Fig. 22.9) are possibly derived via the intermediacy of a geranyllinalyl pyrophosphate (2) precursor. Formation of the allylic ion (50) permits further cyclization to rimuene (51) and abietic acid (52). The former cation (50) can again cyclize to compounds such as phyllocladene (53) and isophyllocladene (Fig. 22.17) (Oehlschlager and Ourisson, 1967). 

Fig. 22.17. Biogenesis of phyllocladene and isophyllocladene (modified from Oehlschlager and Ourisson, 1967),...

Ketone from cafestol, T36.13 17-Norkauran-16-one, T36.1 Phyllocladene norketone, T36.6 5a-Androstan-17-one, T27.13 C19H30O2... 

Terpenoid hydrocarbons Aromatic hydrocarbons Ketones Famasene, pristane, and cyclic hydrocarbons phyllocladene, isophyllocladene, (+)-kaurene isokaurene. etc. Anthracene and phenanthrene type with an attached alkane chain RjCORj Cj5—C3J C291 C31... 

Labdane group cafestol, phyllocladene and related compounds. 

Phthalides, A51 Phthalimides, A9 Phyllocladene, T36 Phyllodulcin, Y6 Phylloquinone, T55 Physalins, T53... 

Alkenes Terpenoid hydrocarbons RjCH = CHR2 Farnasene, pristine, and cyclic hydrocarbons, phyllocladene, isophyllocladene (+) kaurene, and isokaurene, etc. Cj to C33 In algae dienes and tri-enes also found. Branched alkenes might also be minor components... 

Of the isomeric group of tetracyclic diterpenoids originating from the isopi-marenyl cation (Fig. 8.1.24), only two types have been encountered so far. Isohi-baene (451) from Chamaecyparis nootkatensis (93) has already been mentioned. The other type is represented by phyllocladene, known since 1910 (350), but correctly characterized only in 1959. (H-)-Phyllocladanol (462) from the wood of Cryptomeria japonica is an appropriate example for the present discussion (64). Only a few compounds in each class are known at present, and all of these belong to the normal series. 

Briggs L H, Cambie R C, Rutledge P S 1963 Diterpenes. Part VIII. Reaction of epoxides in the (-)-kaurene and phyllocladene series, and a direct correlation of the diterpenes. J Chem Soc 5374-5383... 

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