The red algae genus Laurencia is well known as a source of halogenated sesquiterpenes. From Laurencia nidifica, we isolated fourteen chamigrane derivatives: Two of them are new, accompanied by ten known compounds, and two artifacts. The structures were confirmed by NMR and mass spectroscopy, and compared with spectral data in the literature.

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ABSTRACT:The reaction of 4, 4Ј-dimethoxythiobenzophenone (1a) with tetracyanoethylene (TCNE) afforded an unusual type of 2:1 adduct with the structure of thiacyclopent-2-ene (5a). On the other hand, the reaction of thiobenzophenone (1b) with TCNE afforded the corresponding thiophene, the normal 2:1 adduct (2b). The mechanism of the formation of 5a is discussed.

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