Trisulfide trigger

With the free hydroxyl groups in a suitably protected form, the introduction of the reactive allylic trisulfide triggering device can be addressed. When this advanced stage of the synthesis was reached, it was already known from the work of Magnus37 that the calicheamicin-type allylic methyl trisulfide can be formed upon... 

The S3 unit is also to be found in compounds of natural origin [28, 32, 33]. A very simple one, isolated from an edible mushroom, exhibits both S2 and S3 moieties [34, 35]. 5-Methylthio-l,2,3-trithiane [28] is another example close to charatoxin, and the presence of an allylic trisulfide, and its role as a triggering device for their antitumour activity, in enediyne antibiotics [36,37], is truly astonishing. 

Calicheamicin is a derivative of calicheamicin y, which lacks the trisulfide trigger for stability reasons... 

Research by S.J. Danishefsky et al. has shown that calicheamicin/esperamicin antibiotics containing an allylic trisulfide trigger can undergo a mild Bergman cyclization when treated with benzyl mercaptan." ... 

Magnus, P., Lewis, R., and Bennett, E, Synthetic and mechanistic studies on the antitumor antibiotics esperamicin A and caUcheamicin Oxidative functionalization of the 13-ketobicy-clo[7.3.1]tridecenediyne core structure. Construction of the aHylic trisulfide trigger, 7. Am. Chem. Soc., 114, 2560, 1992. 

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