For over five decades, the solid effect (SE) has been heavily utilized as a mechanism for performing dynamic nuclear polarization (DNP). Nevertheless, it has not found widespread application in contemporary, high magnetic field DNP experiments because SE enhancements display an ω(0)(-2) field dependence. In particular, for nominally forbidden zero and double quantum SE transitions to be partial...

Abbreviations used: Acm, acetamidomethyl; Boc, tert-butoxycarbonyl; Bzl, benzyl; Bzl(4-Me), 4-methylbenzyl; DPDS, di(2-pyridyl)disulfide; DMSO, dimethylsulfoxide; Fmoc, 9-fluorenylmethoxycarbonyl; Mob, 4-methoxybenzyl; Npys, 3-nitro-2-pyridylsulfanyl; Pys, 2-pyridylsulfanyl; StBu, tert-butylsulfanyl; sec, selenocysteine; tBu, tert-butyl; TFA, trifluoroacetic acid; TfOH, trifluoromethanesulfonic...

Contrary to other studies, here we describe cysteine (Cys) pseudoproline-containing peptides with short deprotection times in TFA. The deprotection times fell in the same range as other protecting groups commonly used in SPPS (e.g., 1-3 h). Moreover, when using Cys pseudoprolines as peptide macrocyclization-enhancing moieties a considerable reduction in reaction time was observed compared to a ...

Quantum chemical calculations are used to assess various means of lowering the barrier for the dyotropic rearrangement previously proposed to occur during the carbocation rearrangement process promoted by pentalenene synthase. Several means of lowering this barrier, including a stepwise pathway for dyotropic rearrangement, are uncovered.

Herein we describe our search for a carbocation with a delocalized 5-center 4-electron C- - -H- - -C- - -H- - -C bonding array. Various helical and polycyclic molecular architectures were explored using B3LYP calculations, ultimately leading to cation 8, a remarkable species that possesses two trigonal pyramidal carbons flanking a five-coordinate trigonal bipyramidal carbon.

Reduction of phosphine oxides into the corresponding phosphines using PhSiH3 as a reducing agent and Ph3C+[B(C6F5)4]? an initiator is described. The process highly efficient, broad range secondary tertiary alkyl arylphosphines, bearing various functional groups in generally good yields. reaction believed to proceed through generation silyl cation, which with oxide provides phosphonium salt, fur...

C(CH3)5(+), a pentacoordinate carbocation, was recently described as a "fleeting" molecule, that is, stable only at low temperatures. Herein it is shown using theoretical methods that, owing to carbon tunneling, the molecule is not persistent even at 0 K. One possible way to lengthen its lifespan is by deuterium substitution, in spite of the fact that no bond to hydrogen is broken.