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Praelolide is a new compound which was isolated out from the gorgonian, Menella praelonga (Ridley), collected from the South Sea of China at Zhanjiang, Guangdong. The molecular formula is C_(28) H_(35) O_(12)C1. The research result by X-ray diffraction method on the crystal structure is presented. The compound is orthorhombic with space group P2_12_12, cell dimensions α=16.936, b=16.709, c=10.333, and Z=4. The structure has been solved by direct method and refined to R=0.055 for 2257 unique observable reflexions by least-squares. The molecule is composed of the major conformational isomer in which the three main rings(a six-membered ring, an eight-membered ring, a six-membered ring) take separately the form of chair-chairboat-chair, a five-membered actone ring, a C1 substitution, 4 acetate groups, and a three-membered epoxide ring. The absolute configuration of the molecule has also been determined by statistics (R factor ratio =1.012) and Bijvoet pairs observation. For 30 pairs of the greatest anomalo 相似文献
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长小月二萜内酯(praelolide)是一个新化合物,由产自我国广东省湛江市(石匈)洲岛附近海域的长小月柳珊瑚中分离而得,分子式为C_(28)H_(35)O_(12)Cl。本文用X射线衍射法研究了其晶体结构。此化合物的晶体属正交晶系,空间群为P2_12_12,用直接法测定其结构,取2257个独立可观测反射经最小二乘修正后的R=0.055。分子以六元、八元、六元三个环为主体并以椅-椅船-椅式相拼接而成其主要构象,外接一个五元内酯环,一个氯取代原子,四个醋酸基和一个三元环氧环。用统计法(R因子比=1.012)和Bijvoet反射对观测确定了分子的绝对构型;对30个反常散射贡献最大的Bijvoet反射对,关于第一、第二个对映体的R因子分别为R′( )=0.0517,R′(-)=0.005,后者对应于分子的绝对构型。 相似文献
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