Synthesis of Combinatorial Libraries of Vinylogous Sulfonamidopeptides (vs-Peptides)

Synthesis of sulfonopeptides

Sulfonopeptides as the sulfur analogues of natural peptides have been widely used as enzyme inhibitors due to their tetrahedral sulfonamide moiety, which can mimic the transition-state analogues of hydrolysis of the ester and amide bonds. Synthetic methods of sulfonopeptides are reviewed. The synthetic methods of sulfonopeptides include the condensation of N-protected amino acid/peptide acids and 2-aminoalkanesulfonic acids, coupling of N-protected 2-aminoalkanesulfonyl chlorides and amino acid esters/peptide esters, sulfinylation of amino acid esters/peptide esters with N-protected 2-aminoalkanesulfinyl chlorides and subsequent oxidation, the alkylation of taurine-containing peptides, and the displacement of N-aminoacyl/peptidyl 2-aminoalkyl halides/methanesulfonates with sulfites. Hybrid sulfonophosphinopeptides are prepared through the Mannich-type reaction of N-protected 2-aminoalkanesulfonamides/peptidylsulfonamides, aldehydes, and aryldichlorophosphines/phosphorus trichloride followed by the aminolysis with amino acid/peptide esters or hydrolysis. The developed synthetic methods provide diverse synthetic routes for biologically important sulfonopeptides as the candidates of medicinal agents.

Photolabile Linkers for Solid-Phase Synthesis

Photolabile linkers are the subjects of intense research because they allow the release of the target molecule simply by irradiation. Photochemical release of synthesis products is often facilitated without additional reagents under mild reaction conditions, which may even be environmentally friendly and appealing in the context of greener chemistry. The mild conditions also allow for applications of released material in subsequent biological screening experiments, where contamination with cleavage reagents would be detrimental. This Review pays attention to the increasing number of photolabile linkers developed for solid-phase synthesis and release and covers: (i) o-nitrobenzyloxy linkers, (ii) o-nitrobenzylamino linkers, (iii) α-substituted o-nitrobenzyl linkers, (iv) o-nitroveratryl linkers, (v) phenacyl linkers, (vi) p-alkoxyphenacyl linkers, (vii) benzoin linkers, (viii) pivaloyl linkers, and (ix) other photolabile linkers.

Versatile synthesis of α-substituted taurines from nitroolefins

A series of 1-substituted and 1,1-disubstituted taurines were synthesized from nitroolefins via the Michael addition with sodium ethylxanthate, oxidation with performic acid, and reduction with hydrogen in the presence of palladium on carbon powder. The current route is a versatile and salt-free method for synthesis of both aliphatic and aromatic 1-substituted and 1,1-disubstituted taurines.

Ring-closing metathesis: development of a cyclisation-cleavage strategy for the solid-phase synthesis of cyclic sulfonamides

A series of novel 7-membered cyclic sulfonamides have been synthesised using a solid-phase cyclisation-cleavage RCM strategy. Model solution studies indicated the sulfonamides were suitable substrates for RCM using the Grubbs' catalyst 2. Starting from either 2-carboxyethyl polystyrene (21) or Merrifield resin, various seven-membered sulfonamides were prepared in good to excellent yields at low catalyst loadings (2.5-5 mol%) using a flexible spacer between the polymer and the substrate. In addition, a novel double-armed linker was shown to allow efficient RCM cleavage of sulfonamides with as little as 1 mol% of the ruthenium alkylidene complex 2.

A pentaerythritol-based molecular scaffold for solid-phase combinatorial chemistry

A convergent synthesis has been developed for the preparation of solid-phase bound construct 1, consisting of an orthogonally protected trifunctional core structure that is attached to TentaGel via a photocleavable linker. [structure: see text]

Synthesis of pseudopeptides with sulfoximines as chiral backbone modifying elements

The synthesis of pseudopeptides with a chiral alpha-sulfonimidoylcarboxy moiety in the backbone is described. Starting from readily available (Ss)-S-methyl S-phenyl sulfoximine and various cyclic and acyclic alpha-amino acids the desired products are obtained in good yields with peptide coupling methodology. Specific secondary structures caused by intramolecular hydrogen bonds may be adopted. Results of NMR studies to reveal conformational preferences will be discussed.