Sulfinic Acids and Related Compounds. 13. Unsymmetrical Disulfides Based on Methyl 4-Mercaptobutanesulfinate and 4(S)- or 4(R)-Mercaptoprolines

Article abstract of DOI:10.1021/jo00334a015

In a study of disulfide-sulfinates containing prolylthio moieties epimeric at C-4, the OH group of N-acetylated 4(R)-hydroxy-2(S)-pyrrolidinecarboxylic acid ("trans-4-hydroxy-L-proline", 3) was converted to an epimeric SH group (11) by replacing a 4-O-tosyl group with PhCH2S (to give 5) and debenzylating.Reaction of 11 as the disodium salt with 1,2-dithiane 1,1-dioxide (2) replaced the H of the SH with S(CH2)4SO2Na to give a disulfide-sulfinate salt (9).Since 9 was unstable in solution, with conversion of disodium 4,4'-trithiobis(butanesulfinate) (22) to the diester 23 as a model, 9 was converted to the disulfide-sulfinic ester 10.Subsidiary peaks in the 13C NMR spectra of N-acetyl derivatives were shown to originate from rotamers.Similarly, the epimeric 4(S)-hydroxyproline (16) was converted to the 4(R)-mercaptoproline epimer (19) of 11, which was converted in turn to the disulfide-sulfinate epimer (21) of the sulfinic ester 10.The two disulfide-sulfinate esters 10 and 21 were stable under ambient conditions and began to disproportionate to the two symmetrical disulfides in refluxing ethylacetate in 1.5 (21) to ca. 7 h (10).The sulfinic esters 10, 21, and 23 seem likely to serve as biological precursors of sulfinate and thiolate salts, which may be usefull for several purposes.