(S)-2-Carb-oxy-ethyl l-cysteinyl sulfone

The title compound {systematic name: (2S)-2-aza-niumyl-3-[(2-carb-oxy-ethane)-sulfon-yl]propano-ate}, C₆H₁₁NO₆S, forms enanti-opure crystals in the monoclinic space group P2₁ and exists as a zwitterion, with a protonated α-amino group and a deprotonated α-carboxyl group. Both the carboxyl groups and the amino group are involved in an extensive multicentered inter-molecular hydrogen-bonding scheme. In the crystal, the diperiodic network of hydrogen bonds propagates parallel to (101) and involves inter-connected heterodromic R ₄ ³(10) rings. Electrostatic forces are major contributors to the structure energy, which was estimated by DFT calculations as E _total = -333.5 kJ mol^-1.