Crystal structure of 3-(N.alpha.-tritylmethionyl)benzotriazole 1-oxide, a synthon in peptide synthesis

Structural studies of reagents for peptide bond formation: Crystal and molecular structures of HBTU and HATU

“…1.315 (4) C1-C2 1.384 (4) 1.470 (4) C1-C6 1.375 (4) 1.465 (4) C2-C3 1.365 (4) 1.316 (4) C3-C4 1.408 (5) benzotriazole-l-oxide [11]. A slightly longer distance, 1.303(2)/k, was observed for the analogous bond length in benzotriazole-1-oxide [12]; in that structure the oxygen atom participates as an acceptor atom in a bifurcated hydrogen bond to two water molecules.…”

Structures of Two (E)-3-Substituted Cinnamoylbenzotriazole 1-Oxides

“…Selected bond lengths and angles associated with the triazole ring for the published solvate, [(3)ÁCF 3 CO 2 H](15), are also given. The geometric parameters involved with the triazole rings in 1-3 are in the ranges found for other 3-RC(O)-benzotriazole 1-oxides[19][20][21][22]. Interestingly, the nitrogen oxide, N-O, bond length of 1.291 Å in [(3)ÁCF 3 CO 2 H] is noticeable longer than the corresponding values, between 1.258 and 1.276 Å , found generally in nonsolvated 3-RC(O)-benzotriazole 1-oxides[19][20][21][22], including 1 and 2 [this study].…”

“…The geometric parameters involved with the triazole rings in 1-3 are in the ranges found for other 3-RC(O)-benzotriazole 1-oxides[19][20][21][22]. Interestingly, the nitrogen oxide, N-O, bond length of 1.291 Å in [(3)ÁCF 3 CO 2 H] is noticeable longer than the corresponding values, between 1.258 and 1.276 Å , found generally in nonsolvated 3-RC(O)-benzotriazole 1-oxides[19][20][21][22], including 1 and 2 [this study]. This lengthening of the N-O bond clearly results from the involvement of the oxygen atom in hydrogen bonding with the trifluoroacetic acid solvate.Torsion angles in 1 and 2 are listed in…”

“…A few structures of other N-acyl derivatives, 3-RC(O)-benzotriazole 1-oxides, have been reported. These include compounds having R = Ph 3 CNHCH(CH 2 CH 2 SMe)] [19], [(S)-Ph 3 CNHCH(CH 2 CH 2 CO 2 Me)] [20] and MeOC(Me)= CH [21], MeCH=CHCH=CH- [22]}. The structures of O-acyl derivatives, 1-(RC(O)O)-benzotriazole have also been reported, including compounds with R = Ph 3 CNHCH (CH 2 CHMe 2 ) [23] and R = Ph [24].…”

Study of the Natural Product Intermediates of Steviolbioside, Steviol, and Isosteviol; O‐ and N‐Acylated Forms of Benzotriazoyl Esters

“…3), we observed that 3-int had two geminal protons at d 5.22 and 5.29 (doublet) which is expected to be the two anomeric protons of glucoses and two methyl groups on C 10 tion between the carbon and hydrogen to decide the position order of hydrogen on the aromatic ring. We did not know whether it had another ambiguous amide form 14 (attached to the N2 atom of the benzotriazol ring) on the cyclo-int and 1-3-int NMR charts. Since it was not possible to assign the structure of the N2 amide form unambiguously, we supposed that this amide form (at the N2 atom) might be more-steric hindrance than the other forms (attached to the N1 or N3 atom), especially for the barkyl structures of steviol-, isosteviol-, and steviolbioside intermediates, i.c.,compounds 1-int, 2-int and 3-int, respectively.…”