Cephalotaxine is one compound of five-fused ring structure.
三尖杉碱具有五元稠环结构。
The heterocyele in (4) is a masked fused ring held in abeyance.
中的杂环可以看作是一个被掩蔽的，处于暂时停顿状态的稠环。
In fused-ring and bridged-ring compounds two carbons are common to the two rings.
在稠环和桥环化合物中，两个碳原子是两个环公用的。
Nitrogenous fused-ring derivatives, medicinal compositions containing the derivatives, and use thereof as drugs.
含氮稠环衍生物，含该衍生物的药物组合物，和其作为药物的用途。
Purine a simple nitrogenous organic molecule with a double-ring structure? A 6-membered pyrimidine ring fused to a 5-membered imidazole ring.
一种简单的含氮有机分子，具一个双环结构——六元嘧啶环融合成一个五元咪唑环。
Bicyclic fused aziridines can generate regioselective ring opening reaction with various alcohols, catalyzed by slight concentrated sulfuric acid.
用醇作溶剂、微量的浓硫酸作催化剂，稠合双环氮杂环丙烷衍生物可发生区域选择性氮杂环开环反应。
Conclusion The modification of a 1,4-oxazine-2-one ring fused with positions 9 and 10 of A-ring will reduce the antitumor activity of camptothecins.
结论喜树碱A环的9，10位增加一个“1，4 氧嗪2 酮”六元环后，其抗肿瘤活性要比喜树碱或10 羟基喜树碱的活性降低。
Conclusion The modification of a 1,4-oxazine-2-one ring fused with positions 9 and 10 of A-ring will reduce the antitumor activity of camptothecins.
结论喜树碱A环的9，10位增加一个“1，4 氧嗪2 酮”六元环后，其抗肿瘤活性要比喜树碱或10 羟基喜树碱的活性降低。
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