Kinetics and mechanism of sulfonylation of α-amino acids and dipeptides

Kustova, T.P.; Kochetova, L.B.

Авторы: Kustova T.P., Kochetova L.B.
Журнал: Russian Chemical Bulletin
Том: 68
Номер: 4
Год издания: 2019
Издательство: Springer Nature
Местоположение издательства: Switzerland
Первая страница: 809
Последняя страница: 816
DOI: 10.1007/s11172-019-2489-0
Аннотация: The kinetics of sulfonylation of several -amino acids: Gly, DL-α-Ala, DL-Val, DL-Leu, L-Ile,DL-Thr, DL-Met, DL-Ser, and L-Pro and dipeptides: Gly—Gly, L-α-Ala—L-α-Ala, L-α-Ala—β-Ala,β-Ala—β-Ala in water—propan-2-ol and water—1,4-dioxane binary systems were studied byspectrophotometry. The rate constants for reactions involving -amino acids and dipeptidesvary in a range for 81—52900 L mol–1 s–1 and 1.49—75 L mol–1 s–1, respectively. A considerabledecrease in the rate constants for sulfonylation of dipeptides compared to those of corresponding α-amino acids suggests that the basicity of amino compounds has a signifi cant eff ect ontheir reactivity. The activation parameters of the reactions of amino acids and dipeptides with3-nitrobenzenesulfonyl chloride in aqueous organic media were calculated. The mechanism ofsulfonylation of α-amino acids and the Gly—Gly dipeptide was simulated by constructing thepotential energy surfaces of the gas-phase reactions and taking into account the specifi c solvation of nucleophiles. The processes under study were shown to proceed by the SN2 mechanism,and the reaction pathway that corresponds to the nucleophilic attack along the near-axial direction is more favorable. It was found that the reactions of sulfonyl chlorides with solvatedα-amino acids involve partial desolvation of α-amino acids occuring prior to the formation ofactivated complex.
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