Starting from benzyl 3,5-di-O-benzyl-2-deoxy-1,4-dithio-D-erythro- pentofuranoside (4), the following 2'-deoxy nucleoside analogues have been synthesized: 4'-thiothymidine (8), 3'-azido-4'-thio- deoxythymidine (10), and (E)-5-(2-bromovinyl)-4'-thio-2'-deoxyuridine (22). The first compound is toxic, the second is not toxic nor has detectable biological activity, and the third is not toxic and has significant activity against some herpesviruses.

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Trifluorovinyllithium has been synthesised in high yield from 1,1,1,2-tetrafluoroethane (HFC 134a) by treatment with butyllithium at -78 "C, and then treated with a variety of electrophiles in one-pot reactions.

The formation of lithio derivatives from fluorinated benzenes and fluorinated bromobenzenes has been studied. The bases used were lithium diisopropylamide (LDA) in THF-hexane, butyllithium in diethyl etherhexane and butyllithium in THF-hexane. The lithiated intermediates have been trapped using acetone, to form fluorinated 2-arylpropan-2-ols, or have been warmed to produce benzynes which have been trapped by furan in Diels-Alder additions. The use of LDA allows clean removal of the most acidic proton in the aromatic ring: butyllithium in ether-hexane kings about clean bromine-lithium exchange. In contrast, the use of butyllithium in THF-hexane at -78 "C results in autometallation and the formation of more complex product mixtures. For the formation of the benzynes involved in the Diels-Alder reactions it is necessary to warm the reaction mixtures. When ether-hexane is used as solvent the reactions remain fairly clean, but when THF is added the increasing autometallation again results in more complex reaction mixtures.