Bromonitrin A

The regioisomeric cycloadducts of bromonitrile oxide and N-benzoyl-2,3-oxaza-norborn-5-ene were easily prepared and elaborated into a novel class of uracil-based scaffolds. The key-synthetic step is the nucleophilic substitution at the sp2 carbon atom of the bromoisoxazoline three-dimensional heterocycles. The protocol to perform the nucleophilic substitution of uracil anions was optimized and adapted to the steric requirements of the substrates. A library of pyrimidine derivatives was prepared in very good yields and the products were fully characterized. They are proposed as nucleoside analogues and as synthons for β-turn motifs within PNA structures.

A novel procedure for hydride-induced anionic cyclization has been developed. It includes the reduction of a biaryl bromo-nitrile with a nucleophilic aromatic substitution (S(N)Ar). A range of polysubstituted 6-H-phenanthridines were so obtained in moderate to good yield with good substrate tolerance. This method involves a concise transition-metal-free process and was applied to synthesize natural alkaloids.

d-Glucose was converted into the orthogonally protected open-chain derivative having different blocks at both terminal positions: C1 and C6. Selective deprotection of the C1-position opened a route to intermediate with the D-gluco-configuration, while deprotection at the C6-position gave the L-gulo isomer. In both derivatives, the oxime functionality was installed at the proper terminal position, which produced the corresponding precursors of a family of 7-membered ring iminosugars. One of these oximes was converted into the direct precursor: 6,1-bromonitrile.