To further understand stereoselection in the alkylation of sulfenate anions, a protected cysteinesulfenate was generated in THF solution at low temperature. Introduction of a reactive alkylating agent brings about a cysteinyl sulfoxide in 51-75% yield, with diastereomeric ratios at the sulfinyl group ranging from 83:17 to 95:5. An internally complexed lithium counterion is proposed to account for the stereoselectivity.

In the monoclinic polymorph of the title compound, C13H23NO5S, inter­molecular N—H⋯O hydrogen bonds link mol­ecules into one-dimensional chains along [100]. The atoms of the terminal propenyl group are disordered over two sets of sites with refined occupancies of 0.69 (2) and 0.31 (2).

There are two independent mol­ecules in the asymmetric unit of the title compound, C13H23NO5S. In the crystal structure, inter­molecular N—H⋯O hydrogen bonds link mol­ecules into two independent one-dimensional chains along [100]. The crystal studied was found to be a non-merohedral twin with a ratio of 0.615 (6):0.385 (1) for the refined components. At 200 (1) K [Singh et al. (2009 ▶). Acta Cryst. E65, o1385–o1386] the crystal structure of the title compound contains one disordered mol­ecule in the asymmetric unit of a monoclinic unit cell.