Disulfide linkages, condensation

Ajoene (Spanish, ajo, garlic), 4,5,9-trithiadodeca-l,6,ll-triene-9-oxide 35 (Scheme 12), an antithrombotic compound with other well-defined physiological properties, is formed from allicin.84 Like allicin, ajoene is a sulfoxide but has two further sulfur atoms in a disulfide linkage. E and Z isomeric forms are possible involving the C=C bond at positions 6 and 7. Ajoene is somewhat more stable than allicin. The formation of ajoene probably involves condensation of 2 molecules of allicin forming a sulfonium salt 33, with elimination of propenesulfenic acid. Elimination of a second molecule of propenesulfenic acid... 

Synthesis of polyamides containing disulfide linkages were achieved by condensing 2,2 -dithiobis(acetyl chloride) and 33 -dithiobis(propionyl chloride) with diamines like hexamethylene diamine [143]. The polymers are crystalline and can be drawn into fibers. The disulfide bonds in the main chain are dissociated by mercaptan exchange reactions [144] ... 

The condensation of 1,4-diamines with a variety of carboxylic acid derivatives, e.g. imidate esters, orthoformic esters, /V-ethoxycarbonylthioamides (77JOC2530), nitriles and ethoxyacetylene, produces the cyclic amidine linkage —N = C(R)NH— (67AHC(8)2l, p. 40). Cyclic ureas, —NHC(0)NH—, have been similarly produced using carbonyl chloride, A, A -carbonyldi imidazole, carbon monoxide, thiocarbonyl chloride or carbon disulfide (67AHC(8)21, p. 38). 

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