نتایج جستجو برای: stereoelectronic interactions
تعداد نتایج: 387939 فیلتر نتایج به سال:
The unexpected ability of arylzinc reagents bearing electron-donating substituents to react in a Friedel-Crafts fashion (cine) with electrophiles like perpivaloylated glucoside bromide and benzhydryl bromides in competition with organometallic coupling (ipso) is shown. The stereoelectronic factors required to promote the cine reactivity versus the classical ipso, and the mechanism of this alter...
The first examples of amino acid (Ser/Thr)-sp(2)-iminosugar glycomimetic conjugates featuring an α-O-linked pseudoanomeric linkage are reported. The key synthetic step involves the completely diastereoselective α-glycosylation of Ser/Thr due to strong stereoelectronic and conformational bias imposed by the bicyclic sp(2)-iminosugar scaffold. Mucin-related glycopeptides incorporating these motif...
The potential energy surface of the rearrangement of 3-vinylmethylenecyclobutane to 4-methylenecyclohexene has been studied computationally using density functional theory (B3LYP) and complete active space ab initio methods (CASSCF and CASPT2). The parent reaction is nonconcerted and occurs through several parallel diradical pathways. Transition structures and diradical intermediates are highly...
Two original chiral diphosphines, SYNPHOS and DIFLUORPHOS, have been synthesized on multigram scales. Their steric and electronic profiles have been established in comparison with the commonly used 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl and 6,6'-dimethoxy-2,2'-bis(diphenylphosphino)-1,1'-biphenyl ligands. A screening study of the four ligands in Ru(II)-catalyzed asymmetric hydrogenation of...
Introduction Noncovalent interactions modulate the structure, function, and dynamics of the molecules of life [1]. We have discovered a noncovalent interaction in proteins and nucleic acids, termed the n→π* interaction, in which the lone pair (n) of a donor group (typically a carbonyl oxygen) overlaps with the antibonding orbital (π*) of an acceptor group (typically a carbonyl group) (Figures 1...
Enzymes from Salvia officinalis, capable of catalyzing the electrophilic isomerization and subsequent cyclization of geranyl pyrophosphate (3,8-dimethylocta-2E,6-dienyl pyrophosphate) to the monoterpenes (+)-alpha-pinene and (+)-bornyl pyrophosphate, were examined with a series of substrate analogs modified in carbon chain length and in the geometric and electronic character of the C2-C3 and C6...
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