Diterpenes iodinated

Materials. I-EGF was either made by iodinating mouse EGF (Biomedical Technologies Inc.) by the chloramine T method, to a specific activity of approximately 1-2 Ci/ xmol, using Na- I (Amersham) or purchased from New England Nuclear. Phorbol diterpene esters were purchased from Sigma. Palytoxin was isolated from Palythoa tuberculosa as previously described (1). 

We focused our attention on Tall oil, a by-product of the paper industry, whenever this is prepared according to the KRAFT process. Said material consists of a mixture of highly unsaturated fatty acids (many of which with conjugated diene systems) and terpene derived rosin acids. The rosin acids have the molecular formula C20H30O2 and thus belong to the diterpenes (pimaric and abietic acids). Tall Oil has an iodine number equal to approximately 170 gl2/100 g. 

Williams PG, Yoshida WY, Moore RE, Paul VJ (2003) Novel Iodinated Diterpenes from a Marine Cyanobacterium and Red Alga Assemblage. Org Lett 5 4167... 

Six new kauranoid diterpenes[(62)—(64) and their A -isomers] have been isolated from Sideritis leucantha three (62—64) of them also occur in S. lineari-folia. Foliol (62), sidol (63), and linearol (64) gave the same triacetate, which was isomerized with iodine to the triacetate obtained from isofoliol, isosidol, and isolinearol. These contain the C-15(16) double bond. Foliol was oxidized with chromium trioxide in pyridine to a diketo-aldehyde which was reduced to (— )-kaurene. The location of the oxygen functions at C-3a, C-ip, and C-18 were inferred from the n.m.r. spectrum and from the formation of a 3o ,18-acetonide. 

The hypohalite method of lead tetraacetate and iodine has been applied in the preparation of a key intermediate 18 for the synthesis of labdane diterpene, manool 18a [13]. 

Many terpenes, but rare monoterpenes and not yet sesterterpenes. Sesquiterpenes are particularly abundant and almost all halogenated. The only iodine-containing terpenes currently known are sesquiterpenes isolated from Ceramiales. Then, in order of abundance, diterpenes and triterpenes which are also halogenated in the majority of cases. Many original carbon skeletons without known terrestrial equivalent. 

These iodine-containing diterpenes are not, however, explicitly produced by a Laurencia because the authors say they were isolated from a combination of a cyanobacterium and an rmdetermined red alga. The similarity of the carbon skeleton with those of tasihahdes A and B, nevertheless su ests that the red alga could be a Giga-rtinale or a Ceramiale (Wesley et al., 2003). 

Wesley, P.G., Yoshida, W.Y., Moore, R,E and Paul, V,J. (2003) Novel iodinated diterpenes from a marine cyanobacterium and red alga assemblage. Org. Lett., 5, 4167-4170. 

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