Practical Synthesis of Phosphinic Dipeptides by Tandem Esterification of Aminophosphinic and Acrylic Acids under Silylating Conditions

In this report, a synthetic protocol for the preparation of phosphinic dipeptides of type 5 is presented. These compounds serve as valuable building blocks for the development of highly potent phosphinopeptidic inhibitors of medicinally relevant Zn-metalloproteases and aspartyl proteases. The proposed method is based on the tandem esterification of α-aminophosphinic and acrylic acids under silylating conditions in order to subsequently participate in a P-Michael reaction. The scope of the transformation was investigated by using a diverse set of readily available acrylic acids and (R)-α-aminophosphinic acids, and high yields were achieved in all cases. In most examples reported herein, the isolation of biologically relevant (R,S)-diastereoisomers became possible by simple crystallization from the crude products, thus enhancing the operational simplicity of the proposed method. Finally, functional groups corresponding to acidic or basic natural amino acids are also compatible with the reaction conditions. Based on the above, we expect that the practicality of the proposed protocol will facilitate the discovery of pharmacologically useful bioactive phosphinic 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.