¹³C nuclear magnetic resonance spectroscopy of selected adenine nucleosides: Structural correlation and conformation about the glycosidic bond

Abstract

Structural correlations have been carried out from 13C chemical shifts (δ) and by analysis of 1J(CH) coupling constants, and the conformation about the glycosidic bond has been studied by means of the 3J(CH) vicinal coupling constants between C‐8 and H‐1′ of some adenine nucleosides such as adenosine (Ado), N(7)‐β‐D‐ribofuranosyladenine (N(7)‐Ado), N(9)‐ and N(7)‐β‐D‐xylofuranosyladenine (N(9)‐xylAde and N(7)‐xylAde), N(9)‐(3‐chloro‐3‐deoxy‐β‐D‐xylofuranosyl)adenine (3′‐Cl‐xylAde) and N(9)‐(2‐chloro‐2‐deoxy‐β‐D‐arabinofuranosyl)adenine (2′‐Cl‐araAde). The analysis of the influence on δ13C of the nature and configuration of the substituent in the carbohydrate fragment of the molecule has revealed two types of effects, namely, 1,2‐cis and 1,2‐trans. This approach, as well as the 3J(CH) values and the analysis of the C‐3′‐endo⇌C‐2′‐endo equilibrium of the carbohydrate fragment of nucleosides, and circular dichroism (CD) data, provides important information on the conformation about the glycosidic bond. The magnitudes of 3J(C‐4, H) are indicative of the position of attachment of the carbohydrate fragment to the heterocyclic base.

Combinatorial Synthesis of New Pyrimidine‐ and Purine‐β‐d‐Ribonucleoside Nucleolipids: Their Distribution Between Aqueous and Organic Phases and Their In Vitro Activity Against Human‐ and Rat Glioblastoma Cells In Vitro

“…A comprehensive study of the temperature‐dependent conformation of nucleolipids around their N‐glycosylic bond ( χ , O(4′)–C(1′)–N(1)–C(2) for pyrimidine nucleosides and O(4′)–C(1′)–N(9)–C(4) for purine nucleosides) and its influence on the biomedical activity (SAR study) will be published separately. For this purpose, the 3 J (C,H) couplings 3 J [C(3a)–N(9)–C(1′)–H(1′)] for purine nucleosides and 3 J [C(2)–N(1)–C(1′)–H(1′)] for pyrimidine nucleosides will be determined from temperature‐dependent gated‐decoupled 13 C‐NMR spectra and used for the Lemieux–Akhrem–Mikhailopulo relation . The syn‐anti conformation [torsion angle χ , O(4′)–C(1′)–N(1)–C(2)] of 5‐fluorouridine (NS_4.0.0.0) and its nucleolipids NL_4.4.0.0 and NL_4.4.3.0 are determined from long range 5 J (H–C(1′),F) couplings applying the method of M. Hennig et al …”

“…For this purpose, the 3 J(C,H) couplings 3 J[C(3a)-N(9)-C(1 0 )-H(1 0 )] for purine nucleosides and 3 J[C(2)-N(1)-C(1 0 )-H(1 0 )] for pyrimidine nucleosides will be determined from temperature-dependent gated-decoupled 13 C-NMR spectra and used for the Lemieux-Akhrem-Mikhailopulo relation. [21] [22] The syn-anti conformation [torsion angle v, O(4 0 )-C(1 0 )-N(1)-C(2)] of 5-fluorouridine (NS_4.0.0.0) and its nucleolipids NL_4.4.0.0 and NL_4.4.3.0 are determined from long range 5 J(H-C(1 0 ),F) couplings applying the method of M. Hennig et al [23] The sugar puckering (N/S conformers in %) of the b-D-ribonucleosides and their nucleolipids, listed in Table 1, was estimated from the corresponding 3 J(1 0 ,2 0 ) coupling constants following the empirical eqn (2) according to L. H. Koole et al [24] % South ðSÞ ¼ 3 Jð1 0 ; 2 0 Þ exp: À 1:8=7:0…”

Striking Ability of Adenosine-2′(3′)-deoxy-3′(2′)-triphosphates and Related Analogues to Replace ATP as Phosphate Donor for All Four Human, and theDrosophila Melanogaster, Deoxyribonucleoside Kinases

“…[16,38] Concurrently, the enhanced ability of the former fragment to influence the N $ S pseudorotational equilibria was shown to be lower in the case of purine compounds. The cis-arrangement of the fluorine atom and the phosphate group does not result either in effective steric repulsion, or in additional stabilisation of any conformation, by means of hydrogen bonding.…”

“…[26,38,39] By contrast, the isomeric riboside 6 reveals higher conformational mobility about the glycosidic bond, reflected in identical values of the aforementioned vicinal coupling constants, equal to 3.80 Hz. [26,38,39] By contrast, the isomeric riboside 6 reveals higher conformational mobility about the glycosidic bond, reflected in identical values of the aforementioned vicinal coupling constants, equal to 3.80 Hz.…”

A Novel Route for the Synthesis of Deoxy Fluoro Sugars and Nucleosides

“…Thus, compounds 2, 5, 6, 11, 14, 23, and 27 clearly show fluorination at C(3), whereas 17, 18, and 24 are 2-deoxy-2-fluoro derivatives. The assignments of configuration for most of the compounds synthesized were based primarily on 13 C-NMR data (Table 3), taking into account previous empirical correlations of the effect of configuration of vicinal substituents in the furanose ring on the d(C) values of the atoms bearing these groups [1i] [18].…”