Site-selective S-gem-difluoroallylation of unprotected peptides with 3,3-difluoroallyl sulfonium salts.

Bench-stable 3,3-difluoroallyl sulfonium salts (DFASs), featuring tunable activity and their editable C-ß and gem-difluoroallyl group, proved to be versatile fluoroalkylating reagents for site-selective S-gem-difluoroallylation of cysteine residues in unprotected peptides. The reaction proceeds with high efficiency under mild conditions (ambient temperature and aqueous and weak basic conditions). Various protected/unprotected peptides, especially bioactive peptides, are site-selectively S-gem-difluoroallylated. The newly added gem-difluoroallyl group and other functional groups derived from C-ß of DFASs are poised for ligation with bio-functional groups through click and radical chemistry. This stepwise "doubly orthogonal" modification of peptides enables the construction of bioconjugates with enhanced complexity and functionality. This proof of principle is successfully applied to construct a peptide-saccharide-biotin chimeric bioconjugate, indicating its great potential application in medicinal chemistry and chemical biology.

Late-stage gem-difluoroallylation of phenol in bioactive molecules and peptides with 3,3-difluoroallyl sulfonium salts.

An efficient method for the late-stage selective O-fluoroalkylation of tyrosine residues with a stable yet highly reactive fluoroalkylating reagent, 3,3-difluoroallyl sulfonium salts (DFASs), has been developed. The reaction proceeds in a mild basic aqueous buffer (pH = 11.6) with high efficiency, high biocompatibility, and excellent regio- and chemoselectivity. Various oligopeptides and phenol-containing bioactive molecules, including carbohydrates and nucleosides, could be selectively O-fluoroalkylated. The added vinyl and other functional groups from DFASs can be valuable linkers for successive modification, significantly expanding the chemical space for further bioconjugation. The synthetic utility of this protocol has been demonstrated by the fluorescently labeled anti-cancer drug and the synthesis of O-link type 1,4,7,10-tetraazacyclododecane-N,N',N,N'-tetraacetic acid-tyrosine3-octreotate (DOTA-TATE), showing the prospect of the method in medicinal chemistry and chemical biology.

3,3-Difluoroallyl Sulfonium Salts: Practical and Bench-Stable Reagents for Highly Regioselective gem-Difluoroallylations.

The site-selective introduction of the difluoromethylene group into organic molecules has important applications in producing pharmaceuticals and agrochemicals. However, the general and efficient methods that can construct both C(sp2 )-CF2 R and C(sp3 )-CF2 R bonds remain challenging. Here, we disclose a new type of practical and bench-stable difluoroalkylating reagent 3,3-difluoroallyl sulfonium salt (DFAS) that can be practically prepared from inexpensive and bulk chemical feedstock 3,3,3-trifluoropropene. This reagent allows highly regioselective gem-difluoroallylation of various organozinc reagents, including aryl, primary, secondary, and tertiary alkyl zinc reagents, via copper catalysis under mild reaction conditions with high efficiency. The reaction can also be extended to a series of substituted DFASs. Application of the approach leads to the short synthesis of complex analogs, showing the prospect of DFASs in medicinal chemistry.