Chemical Structure of New Marine Diterpenes and Control of Their Biosynthesis

1.棕藻Dictyota dichotoma中新二萜化合物的分离和结构鉴定从北海道Oshyoro海湾采集的褐藻提取物中分离得到22个新的二萜化合物，并对其结构进行了鉴定。结果表明，该藻可产生多种官能团排列的双环和三环二萜类化合物。它们的所有骨架都被认为是由异丙烯基吉马三烯衍生而来。此外，在褐藻中发现的一种抗真菌物质被证明是已知的化合物二羟基酚C。这是第一个显示出抗真菌活性的羟基氢天青烯。通过X-射线单晶分析确定了二氯苯酚的绝对构型。核磁共振分析和分子力学计算表明，二氢呋喃T的9元环几乎固定在一个稳定的构象上，二氢异丙酚在两个稳定构象之间保持平衡。Dictyota dichotoma中发现的二萜类化合物的生物发生根据新确定的二苯基苯酚的绝对构型，提出了Dictyota dichotoma中发现的各种骨架的生物发生途径。从红藻Laurencia obtus.中分离出具有细胞毒性的三萜化合物新的三萜环醚、叔丁烯和百里香-23-乙酸酯，并对其结构进行了鉴定。后者及其部分衍生物在体外对P388细胞具有显著的细胞毒作用。

1. Isolation and structure dertermination of new and antifungal diterpenes of the brown alga, Dictyota dichotomaFrom hydrophobic fractions of the extract of the alga collected at Oshyoro bay, Hokkaido, 22 new diterpenes were isolated and their structures were determined. It was found that the alga produced various bicyclic and tricyclic diterpenes with many kinds of functional group arrangements. All of their skeletons were considered to be derived from prenylated germacratriene. Furthermore, an antifungal substance found in the brown alga was shown to be the known compound dictyol C. It was the first hydroxy hydroazulene exhibiting antifungal activity. The absolute configuration of dilophol was determined by X-ray crystallographic analysis. Nmr analysis and molecular mechanics calculations revealed that the 9 membered ring of dictyofuran T was almost fixed at a stable conformation and dilophol was equilibrated between two stable conformations.2. Biogenesis of the diterpenes found in Dictyota dichotomaBased mainly on the newly determined absolute configuration of dilophol, the biogenetic routes for the various skeletons found in the diterpenes of D. dichotoma were proposed.3. Cytotoxic triterpenes isolated from the red alga, Laurencia obtusaNew triterpene cyclic ethers, teurilene and thyrsiferyl-23-acetate were isolated and their structures were determined. The latter and some of its derivatives showed remarkable cytotoxic property against P388 in vitro cell line.