Crystal structure of seleno-l-cystine di­hydro­chloride

Numerous crystal structures are available for the dimeric amino acid cystine. In proteins it is formed by oxidation of the –SH thiol groups of two closely spaced cysteine residues, resulting in the formation of a familiar di­sulfide bridge. The title compound [systematic name: (R,R)-1,1′-dicarb­oxy-2,2′-(diselanedi­yl)diethanaminium dichloride], C(6)H(14)N(2)O(4)Se(2) (2+)·2Cl(−), is the first example of a small mol­ecule structure of the biologically important analogue with a —CH(2)—Se—Se—CH(2)— bridging unit. Bond lengths and angles of seleno-l-cystine di­hydro­chloride and its isotypic sulfur analogue l-cystine di­hydro­chloride are compared.