第四为稠环化合物（萘）；

The fourth is cyclic compounds (naphthalene).

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在稠环和桥环化合物中，两个碳原子是两个环公用的。

In fused-ring and bridged-ring compounds two carbons are common to the two rings.

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近来的报道表明某些氮桥稠杂环化合物还有抗肿瘤和抗hiv的功效。

In the recent report, some of these N-bridged heterocycles also can kill the tumour cell and the HIV.

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近来的报道表明某些氮桥稠杂环化合物还有抗肿瘤和抗hiv的功效。

In the recent report, some of these N-bridged heterocycles also can kill the tumour cell and the HIV.

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