Traceless Release of Alcohols Using Thiol-Sensitive Oxanorbornadiene Linkers

A class of ester-amide oxanorbornadiene (EA-OND) molecules was developed to release alcohol cargos by succinimide formation upon addition of a thiol reagent. The resulting ring-closed adducts undergo further fragmentation by retro-Diels-Alder reaction to release a furan moiety in a manner similar to oxanorbornadiene diesters. The rates of each of these fragmentation pathways in the same medium were found to be sensitive to the steric nature of the amide substituent. Alcohol release was much faster in protic solvents than in aprotic ones, suggesting that this system may be useful for rapid response to thiols in biological environments. Accordingly, the attachment and thiol-dependent release of cholesterol was characterized as an example of the manipulation of a drug-like cargo.