Stable,fonimidate has been prepared in high yield by direct O-ethylation of N-tert-butyl-4-nitrobenzenesulfonamide with iodoethane and silver(I) oxide in dichloromethane. This sulfonimidate directly ethylates various acids to esters; the stronger the acid, the faster it alkylates and in higher yield. It readily ethylates alcohols and phenols to ethers at room temperature in the presence of tetrafluoroboric acid catalyst without molecular rearrangements or racemization. We have defined these reactions as SNAAP alkylations: [substitution, nucleophilic of acids, alcohols and phenols]. The hard sulfonimidate alkylating agent is chemoselective, preferring oxygen > nitrogen > sulfur. The sulfonamide byproduct of alkylation is readily recycled to the sulfonimidate.

Cleavage of DNA at noncanonical recognition sequences by restriction endonucleases (star activity) in bulk solution can be promoted by global experimental parameters, including enzyme or substrate concentration, temperature, pH, or buffer composition. To study the effect of nanoscale confinement on the noncanonical behaviour of BamHI, which cleaves a single unique sequence of 6 bp, we used AFM nanografting to generate laterally confined DNA monolayers (LCDM) at different densities, either in the form of small patches, several microns in width, or complete monolayers of thiol-modified DNA on a gold surface. We focused on two 44-bp DNAs, each containing a noncanonical BamHI site differing by 2 bp from the cognate recognition sequence. Topographic AFM imaging was used to monitor end-point reactions by measuring the decrease in the LCDM height with respect to the surrounding reference surface. At low DNA densities, BamHI efficiently cleaves only its cognate sequence while at intermediate DNA densities, noncanonical sequence cleavage occurs, and can be controlled in a stepwise (on/off) fashion by varying the DNA density and restriction site sequence. This study shows that endonuclease action on noncanonical sites in confined nanoarchitectures can be modulated by varying local physical parameters, independent of global chemical parameters.

significantly to the free energy and extend the interaction beyond the electrostatic range of the molecules. Such long-range water effects could potentially be of great importance to many biological systems, in which molecules appear to be able to recognize each other across significant distances, or for which the kinetic rates are too fast to be due to pure diffusion. Our results are in good agreement with experiments on the role of solvent in DNA condensation by multivalent cations.