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Arenediazonium o -benzenedisulfonimides 3 (20 examples, yield >90%) were prepared in the dry state by diazotization of aromatic amines with i -pentyl nitrite and o -benzenedisulfonimide in glacial acetic acid or formic acid at 0-5°C. Unlike most diazonium salts in the dry state, salts 3 are very highly stable.

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Abstract:The conformational preferences of the alicyclic C","-disubstituted glycines Ac,c (I-amino-I-cycloalkane-carboxylic acid; n = 4 , 7, 9, 1 2 ) were assessed in selected model compounds, including homopeptides and Ala (or Aib, a-aminoisobutyric acid) lAc,c peptides containing a small total number of residues, by Fourier transform ir absorption, 'H-nmr, and x-ray diffraction analyses. The results obtained indicate that p-turn and 310-helicalstructures are preferentially adopted by short peptides rich in these cycloaliphatic a-amino acids.

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The structural prototype of a new generation of regioselectively addressable functionalized templates (RAFTs) for use in protein de novo design has been synthesized and crystallized. The structure of the aromatically substituted cyclodecapeptide was determined by X-ray diffraction; it consists of an antiparallel beta sheet spanned by heterochirally induced type IIprime prime or minute beta turns, similar to that observed in gramicidin S. The three-dimensional structure of the artificial template was also examined by an NMR spectroscopic analysis in solution and shown to be compatible with a beta-sheet plane suitable for accommodating secondary functional peptide fragments for the synthesis of template-assembled synthetic proteins (TASPs).