Synthesis and characterization of selenium(I/II) and tellurium(IV) derivatives of amino acids

The direct reaction between Te metal and methyl 2-(2-bromoacetamido)propanoate (27) at room temperature, yields the first example of organotellurium(IV) derivative (MeOC(O)CH(Me)NHCOCH2)(2)TeBr2 (31). Similarly, reaction of Te with methyl 2-(2-bromoacetamido)acetate (26) and methyl 2-(2-bromoacetamido)-3-phenylpropanoate (28) in presence of Nal in acetone gives MeOC(O)CH(2)NHCOCH2l (29), MeOC(O)CH(R)NHCOCH2)(2)Tel(2) (R = H (30) and CH2Ph (32). Treatment of 26/27/28 with Li2Te2/Li2Se2 readily provides the [MeOC(O)CH(CH3)NHCOCH2](2)Te-2, (33); [MeOC(O)CH2NHCOCH2](2)Se-2, (34); [MeOC(O)CH(CH2Ph)NHCOCH2](2)Se-2, (35) and [GRAPHICS] (36). Similarly the reaction of (2,6-dimethyl-4-tert-butylC(6)H(2))SeNa with 28 readily provide the [MeOC(O)CH(CH2Ph) NHCOCH2]SeC6H2-2,6-dimethyl-4-tert-butyl), (37) in good yield. Molecule [MeOC(O)CHNH(Boc)CH2](2)Se-2, (38) and [NaOC(O)CHNH(Boc)CH2Te(2,4,6-Me3C6H2] (39) were prepared by the treatment of Li 2 Se 2 /2,4,6-Me3C6H2TeNa with methyl 3-bromo-2-((tert-butoxycarbonyl)amino)propanoate and N-(t-Boc)-L-serine beta-lactone respectively. These compounds are purified by chromatography and characterized by a number of analytical techniques such as (H-1, C-13, Se-22 and Te-125 NMR) spectroscopy, mass spectrometry and elemental analysis. The single crystal X-ray studies of 29, 30, 31, 36 and 38 revealed the presence of characteristic O center dot center dot center dot Se/Te, secondary bonding interactions. A detailed analysis of the crystal structures of the compound reveals interesting supramolecular assembly. (C) 2018 Elsevier B.V. All rights reserved