Isonitrin

In studies directed towaids the synthesis of the fungal isonitrile antibiotic isonitrin B (103), a cy-clopentanoid metabolite related to trichoviridine (104), various trialkylsilyl enol ethers were irradiated with propionaldehyde to produce equimolar amounts of stereoisomeric bicyclic oxetanes (105). The corresponding silyl dienol ethers, however, gave little oxetane product owing to preferential diene photopolymerization. The use of vinyl epoxide derivatives such as (106), however, offers a possible access to the epoxycyclopentanoid system with simultaneous control of the face selectivity of the photoaddition by the epoxide moiety. 

The first enantioselective synthesis of (—)-isonitrin B 1670, the parent of a small family of isonitrile antibiotics having compact but highly functionalized (and highly reactive) cydopentane rings, has been described [1240]. In the penultimate reaction step, the corresponding formamide is dehydrated with triflic anhydride forming the O-protected isocyanide in 52% yield deprotection affords (—) -isonitrin B 1670 in 68% yield. 

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