<sup>15</sup>N‐NMR‐Spektroskopie — neue Methoden und ihre Anwendung

Philipsborn, W. Von; Müller, Raffaello

doi:10.1002/ange.19860980504

Cited by 63 publications

(10 citation statements)

References 195 publications

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“…This result is in line with findings reported for anomeric 5-aza-7-deaza-2'-deoxyguanosine [29]. As "N-NMR spectroscopy offers more precise insight into the electronic grounds and chemical behavior than 'H-and I3C-NMR spectra [30], we have measured the "N-NMR spectra of tubercidin (lo), 2'-deoxytubercidin (12), as well as of their precursors and related nucleosides (Table 5 ) . "N-NMR Spectra.…”

Section: I3c'h Coupling Constants [Hz] Of Compounds 6a and 7a A)b)supporting

confidence: 91%

ChemInform Abstract: Stereoselective Synthesis of Pyrrolo(2,3‐d)pyrimidine α‐ and β‐D‐Ribonucleosides from Anomerically Pure D‐Ribofuranosyl Chlorides: Solid‐Liquid Phase‐Transfer Glycosylation and 15N NMR Spectra.

Rosemeyer

Seela

1988

ChemInform

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Solid-liquid phase-transfer glycosylation (KOH, tris[2-(2-methoxyethoxy)ethyl]amine ( = TDA-I ), MeCN) of pyrrolo[2,3-djpyrimidines such as 3a and 3b with an equimolar amount of 5-U-[( 1, I-dimethylethy1)dimethylsilyl~-2,3-U-(l-methylethylidene)-a -D-ribofuranosyl chloride (1) [6] gave the protected 8-o-nucleosides 4a and 4b, respectively, stereoselectively (Scheme). The B-o-anomer 2 [6] yielded the corresponding a -D-nucleosides 5a and 5b with traces of the 8-D-compounds. The 6-substituted 7-deazapurine nucleosides 6a, 7a, and 8 were converted into tubercidin (10) or its a -D-anomer (1 1). Spin-lattice relaxation measurements of anomeric ribonucleosides revealed that T , values of H-C(8) in the a-o-series are significantly increased compared to H-C(8) in the B-D-series while the opposite is true for T , of H-C(1'). I5N-NMR data of 6-substituted 7-deazapurine o-rihofuranosides were assigned and compared with those of 2'-deoxy compounds. Furthermore, it was shown that 7-deaza-2'-deoxyadenosine ( = 2'-deoxytubercidin; 12) is protonated at N( l), whereas the protonation site of 7-deaza-2'-deoxyguanosine (20) is N(3).Introduction. -Pyrrolyl anions have been proved to be effective in regioselective glycosylation of pyrrolo[2,3-d]pyrimidines. They were employed first by Goto during the synthesis of queosine and were generated with NaH [ 11.In 1983, the synthesis of 7-deazaguanosine and -inosine has been reported by our laboratory using liquid-liquid phase-transfer conditions for anion generation and employing benzyl-protected D-ribofuranosyl bromide during glycosylations [24]. According to the configuration of the bromo sugar, predominant formation of a -D-configurated glycosylation products was observed (a //? 5 : 2). Nevertheless, it was recognized that glycosylation proceeded stereoselectively and was controlled by the anomeric ratio of halogenoses present in the reaction mixture. Unfortunately, it was not possible to generate the anomerically pure bromo sugar separately. Moreover, all attempts to use acyl-protected halogenoses failed. While acyloxonium ions are formed as intermediates, nucleophilic attack of the nucleobase resulted in orthoamides which were not rearranged to nucleosides [ 51. As a consequence, neighbouring-group participation which directs the incoming nucleobase into the /?-face cannot be exploited.Recently, Wilcox and coworkers have described the preparation of a -and /?-D-configurated 2,3-U-isopropylidene-5-0-[(terf-butyl)dimethylsilyl]-~-ribofuranosyl chlorides 1 and 2, respectively [6]. As these halogenoses can be prepared as pure anomers and do not contain a participating substituent at C(2), we have employed them for the synthesis of pyrrolo[2,3-d]pyrimidine D-ribofuranosides. In the following, we describe the stereoselective synthesis of either /?-or a -D-configurated tubercidin (10 and 11, resp.) employing the halogenose 1 or 2 upon solid-liquid phase-transfer glycosylation. As now pyrrolo[2,3-d]pyrimidine D-ribonucleosides as well as 2'-deoxy-~-ribonucleosides are available in sufficient...

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Section: I3c'h Coupling Constants [Hz] Of Compounds 6a and 7a A)b)supporting

confidence: 91%

ChemInform Abstract: Stereoselective Synthesis of Pyrrolo(2,3‐d)pyrimidine α‐ and β‐D‐Ribonucleosides from Anomerically Pure D‐Ribofuranosyl Chlorides: Solid‐Liquid Phase‐Transfer Glycosylation and 15N NMR Spectra.

Rosemeyer

Seela

1988

ChemInform

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“…[10b,11a,11b,12b,12c,13a,13c,15a,15b] In 15 N, 1 H-HMBC NMR experiments a signal at δ = 160.7 ppm, that is attributed to the nitrilium nitrogen atom, is observed. In comparison to uncoordinated imines [14a,14b] as well as nitriles [17] this signal is shifted to higher field but in good agreement with other known nitrilium ions. [13a,18] Single crystals of 2 suitable for X-ray diffraction can be obtained by slow evaporation of a solution in benzene.…”

Section: Resultssupporting

confidence: 74%

Imines in the Titanium Coordination Sphere - Transformation of Imidoyl Chlorides to Nitrilium Ions

Loose

Schmidtmann

Beckhaus

2017

Z. Anorg. Allg. Chem.

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In the reaction of TiCl4 in benzene as solvent with the imidoyl chloride p‐Tolyl(Cl)C=NPh (1) the abstraction of the chloride substituent is observed, leading to the nitrilium salt [p‐Tolyl–C≡N–Ph]+[Ti2Cl9]– (2) in quantitative yield. The highly electrophilic salt 2 is characterized by IR‐ and NMR spectroscopy. The observed band for the C≡N stretching mode of 2 clearly indicates the formation of a nitrilium ion. Especially a characteristic line broadening of the 13C{1H}‐NMR signals related to carbon atoms next to the nitrogen is observed. By 15N,1H‐HMBC NMR experiments it is shown that the nitrogen signal of 2 is significantly shifted to high‐field in relation to nitriles and imines. The molecular structure of 2 was confirmed by single‐crystal X‐ray diffraction. The C≡N bond length and the linearity of the C–C≡N–C unit in 2 confirm the triple bond character of this bond.

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“…As external standard 15 N-enriched ammonium nitrate (98%, Sigma-Aldrich) in D 2 O was used ( 3.90 ppm). 12 The data obtained are summarized in Table 1. Analysis of the spectra obtained in dimethyl sulfoxide is straightforward; see Fig.…”

Section: Nmr Measurementsmentioning

confidence: 99%

Characterization of biguanides by15N NMR spectroscopy

Clement

Girreser

1999

Magn. Reson. Chem.

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¹⁵N‐NMR‐Spektroskopie — neue Methoden und ihre Anwendung

Cited by 63 publications

References 195 publications

ChemInform Abstract: Stereoselective Synthesis of Pyrrolo(2,3‐d)pyrimidine α‐ and β‐D‐Ribonucleosides from Anomerically Pure D‐Ribofuranosyl Chlorides: Solid‐Liquid Phase‐Transfer Glycosylation and 15N NMR Spectra.

ChemInform Abstract: Stereoselective Synthesis of Pyrrolo(2,3‐d)pyrimidine α‐ and β‐D‐Ribonucleosides from Anomerically Pure D‐Ribofuranosyl Chlorides: Solid‐Liquid Phase‐Transfer Glycosylation and 15N NMR Spectra.

Imines in the Titanium Coordination Sphere - Transformation of Imidoyl Chlorides to Nitrilium Ions

Characterization of biguanides by15N NMR spectroscopy

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15N‐NMR‐Spektroskopie — neue Methoden und ihre Anwendung

Cited by 63 publications

References 195 publications

ChemInform Abstract: Stereoselective Synthesis of Pyrrolo(2,3‐d)pyrimidine α‐ and β‐D‐Ribonucleosides from Anomerically Pure D‐Ribofuranosyl Chlorides: Solid‐Liquid Phase‐Transfer Glycosylation and 15N NMR Spectra.

ChemInform Abstract: Stereoselective Synthesis of Pyrrolo(2,3‐d)pyrimidine α‐ and β‐D‐Ribonucleosides from Anomerically Pure D‐Ribofuranosyl Chlorides: Solid‐Liquid Phase‐Transfer Glycosylation and 15N NMR Spectra.

Imines in the Titanium Coordination Sphere - Transformation of Imidoyl Chlorides to Nitrilium Ions

Characterization of biguanides by15N NMR spectroscopy

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¹⁵N‐NMR‐Spektroskopie — neue Methoden und ihre Anwendung