We investigate L-Tyrosine as an efficient catalyst for the Knoevenagel condensation of arylaldehydes with meldrum’s acid containing cyclic active methylene group in solvent-free condition under grindstone method at room temperature to produce substituted-5-benzylidene-2,2-dimethyl-[1,3]dioxane-4,6-diones 3(a–j).

The S-acetamidomethyl (Acm) or trityl (Trt) protecting groups are widely used in the chemical synthesis of peptides that contain one or more disulfide bonds. Treatment of peptides containing S-Acm protecting group with iodine results in simultaneous removal of the sulfhydryl protecting group and disulfide formation. However, the excess iodine needs to be quenched or adsorbed as quickly as possible after completion of the disulfide bond formation in order to minimize side reactions that are often associated with the iodination step. We report here a simple method for simultaneous quenching and removal of iodine and isolation of disulphide bridge peptides. The use of excess inexpensive anion exchange resin to the oxidized peptide from the aqueous acetic acid/methanol solution affords quantitative removal of iodine and other color impurities. This improves the resin life time of expensive chromatography media that is used in preparative HPLC column during the purification of peptide using preparative HPLC. Further, it is very useful for the conversion of TFA salt to acetate in situ. It was successfully applied commercially, to the large scale synthesis of various peptides including Desmopressin, Oxytocin, and Octreotide. This new approach offers significant advantages such as more simple utility, minimal side reactions, large scale synthesis of peptide drugs, and greater cost effectiveness.

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L-Tyrosine has been utilized as an efficient and eco-friendly catalyst for the Knoevenagel condensation of arylaldehydes 1(a-k) with barbituric acid and 2-thiobarbituric acid containing cyclic active methylene groups in aqueous medium at room temperature to produce 5-arylidene-pyrimidine-2,4,6-triones and 5-arylidene-2-thioxo-dihydro-pyrimidine-4,6-diones 3(a-p).

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