Dipyrazolo[1,5-a:4',3'-c]pyridines – a new heterocyclic system accessed via multicomponent reaction

• Wolfgang Holzer,
• Gytė Vilkauskaitė,
• Eglė Arbačiauskienė and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2012, 8, 2223–2229, doi:10.3762/bjoc.8.251

• multicomponent reaction affording new tricyclic compounds with a dipyrazolo[1,5-a:4',3'-c]pyridine core. Detailed NMR spectroscopic investigations (1H, 13C and 15N) were undertaken with all obtained compounds. Keywords: cyclization; nitrogen heterocycles; NMR spectroscopy; multicomponent reaction; pyrazole

• (95.1–98.3 ppm), C-9 (5j: C-10a, 5k,l: C-11a) (105.6–114.6 ppm), C-9a (5j: C-10b, 5k,l: C-11b) (130.4–134.2) and C-9b (5j: C-10c, 5k,l: C-11c) (111.2–112.7 ppm). The other carbon resonances (C-1, C-5, C-8) are influenced by the attached substituents to a somewhat larger extent. Also the 15N NMR spectra

• show a uniform pattern: the resonances of N-2 and N-3 are slightly influenced by the substituent at position 1 with the 1-H derivatives having slightly larger chemical shifts than those of the corresponding 1-methyl congeners. The 15N chemical shifts of N-6 and N-7 are somewhat smaller with derivatives

Conformational analysis, stereoelectronic interactions and NMR properties of 2-fluorobicyclo[2.2.1]heptan-7-ols

• Fátima M. P. de Rezende,
• Marilua A. Moreira,
• Rodrigo A. Cormanich and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2012, 8, 1227–1232, doi:10.3762/bjoc.8.137

• exhibits F∙∙∙HO intramolecular HB, is substantially higher, i.e., (−)28.4 Hz [9]. In fact, the importance of NMR scalar spin–spin coupling constants (SSCCs) transmitted through hydrogen bonds emerged, fundamentally, from the observation of 1hJ15N,H and 2hJ15N,15N SSCCs for DNA and RNA molecular systems [10

Identification and isolation of insecticidal oxazoles from Pseudomonas spp.

• Florian Grundmann,
• Veronika Dill,
• Andrea Dowling,
• Aunchalee Thanwisai,
• Edna Bode,
• Narisara Chantratita,
• Richard ffrench-Constant and
• Helge B. Bode

Beilstein J. Org. Chem. 2012, 8, 749–752, doi:10.3762/bjoc.8.85

• order to confirm the oxazole structures and to reveal their biosynthesis. Therefore, both strains were cultivated in fully labeled 13C or 15N media and 12C precursors were added (Figure 2). Five carbons of leucine are incorporated in compound 3, while eight carbons of compound 5 originate from

• intermediates of the oxazole syntheses (12–27) are also shown as they were also tested for their biological activity. MS data from strain PB22.5, which was cultivated in [U-13C] and [U-15N] medium background and LB medium as a control. Feeding experiments with 12C and 14N amino acids confirmed structures 3 and

Chemo-enzymatic modification of poly-N-acetyllactosamine (LacNAc) oligomers and N,N-diacetyllactosamine (LacDiNAc) based on galactose oxidase treatment

• Christiane E. Kupper,
• Ruben R. Rosencrantz,
• Birgit Henßen,
• Helena Pelantová,
• Stephan Thönes,
• Anna Drozdová,
• Vladimir Křen and
• Lothar Elling

Beilstein J. Org. Chem. 2012, 8, 712–725, doi:10.3762/bjoc.8.80

• AVANCE III 600 MHz spectrometer (600.23 MHz for 1H, 150.93 MHz for 13C, and 60.82 MHz for 15N) in D2O at 30 °C. The residual signal of the solvent was used as an internal standard (δH 4.508). The carbon spectra were referenced to the signal of acetone (δC 30.50). 1H NMR, 13C NMR, COSY, HSQC, HMBC, HSQC

• shift of the involved carbons (C-4 for Glc, C-3 for Gal). The structure of 15b was supported by the 1H,15N HMBC experiment. The extracted 1H,15N contacts of seven nitrogen atoms (see the Table NMR 7 in Supporting Information File 2) confirmed the connection of particular spin systems; the remaining

Chemistry of polyhalogenated nitrobutadienes, 10: Synthesis of highly functionalized heterocycles with a rigid 6-amino-3-azabicyclo[3.1.0]hexane moiety

• Viktor A. Zapol’skii,
• Jan C. Namyslo,
• Armin de Meijere and
• Dieter E. Kaufmann

Beilstein J. Org. Chem. 2012, 8, 621–628, doi:10.3762/bjoc.8.69

• -dimensional, direct detection) and an inverse-detected 1H/15N-HMBC gave the nitrogen shifts (internal MeNO2 at 0.0 ppm): −65.8 ppm (C=N), −244.2 ppm (NCO), and −319.5 ppm (NBn). In addition to the twofold triazole substitution, the nitrodiene 3 was treated with four equiv of benzotriazole in THF. Thus, the

NMR studies of anion-induced conformational changes in diindolylureas and diindolylthioureas

• Damjan Makuc,
• Jennifer R. Hiscock,
• Mark E. Light,
• Philip A. Gale and
• Janez Plavec

Beilstein J. Org. Chem. 2011, 7, 1205–1214, doi:10.3762/bjoc.7.140

• mechanics calculations. NOE experiments showed that the anti–anti conformer along the C7–N7α bonds was predominant in DMSO-d6 solution in the absence of anions. Anion-induced changes in the 1H and 15N chemical shifts confirm the weak binding of chloride anions with negligible conformational changes. Strong

• , shown in Figure 1, were evaluated by means of NMR spectroscopy. Proton and 13C NMR resonances were assigned through 1D and 2D spectra, while 15N chemical shifts were determined by 1H–15N correlations in HSQC and HMBC spectra. Notable 1H and 15N NMR chemical shifts of 1–4 are shown in Table 2. It should

• ), possibly due to a more efficient conjugation. 1H and 15N NMR chemical shift changes in 1 upon addition of anions Figure 2 shows 1H chemical shift changes of 1 in the presence of one equivalent of chloride, acetate, benzoate, bicarbonate and dihydrogen phosphate anions. The protons that are most affected by

Unusual behavior in the reactivity of 5-substituted-1H-tetrazoles in a resistively heated microreactor

• Bernhard Gutmann,
• Toma N. Glasnov,
• Tahseen Razzaq,
• Walter Goessler,
• Dominique M. Roberge and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2011, 7, 503–517, doi:10.3762/bjoc.7.59

• from the resulting azido group and a subsequent 1,2-migration of the acylimido group from carbon to nitrogen to give the same nitrilimine intermediate was ruled out by Herbst via 15N labeling studies [44]. The degradative acylation of 5-substituted-1H-tetrazoles with acyl halides is in fact an elegant

A practical synthesis of the ¹³C/¹⁵N- labelled tripeptide N-formyl- Met-Leu-Phe, useful as a reference in solid- state NMR spectroscopy

• Sven T. Breitung,
• Jakob J. Lopez,
• Gerd Dürner,
• Clemens Glaubitz,
• Michael W. Göbel and
• Marcel Suhartono

Beilstein J. Org. Chem. 2008, 4, No. 35, doi:10.3762/bjoc.4.35

• 13C/15N-labelled tripeptide 1 could be isolated in a typical batch. This peptide can be easily crystallised and is therefore well suited as a standard sample for setting up solid-state NMR experiments. Keywords: Fmoc solid phase peptide synthesis; formylation; f-MLF; magic-angle spinning; Wang resin

• ; Introduction There appears to be a general lack of widely available and standardised samples for setting up new solid-state NMR experiments. Such a standard sample should show a small 13C and 15N linewidth and a short 1H T1 relaxation time. It should contain a number of molecular groups with different chemical

• shifts for setting up correlation spectra. The 13C/15N-labelled tripeptide N-formyl-Met-Leu-Phe-OH (f-MLF-OH) (1) has been shown in a number of solid-state NMR studies to fulfil these criteria. It has been used in great detail to examine spin dynamics in peptide and for distance measurements [1][2][3][4