Meisenheimer spiro picryl complex of adenosine. Example of a stereoselective dioxolane ring opening in an acidic medium

Abstract

and 13C NMR studies show that the acidic decomposition of the spiro Meisenheimer picryl complex of adenosine (2a) in aqueous and in dimethyl sulfoxide solutions gives 3'-0-(2,4,6-trinitrophenyl)adenosine (3a), the opening of the dioxolane ring of 2a occurring exclusively at the 02' oxygen. In agreement with the chirality of the ribose ring, the two sides of the cyclohexadienyl ring of the spiro complex 2a are inequivalent. However, the large anisochrony observed in and 13C spectra also reflects the steric inhibition of resonance of the endo 6"-nitro group. Vicinal proton-proton coupling constants indicate the ribose ring to be essentially flattened in the complex 2a but to exist chiefly as the type S conformer in the ether 3a. In dimethyl sulfoxide-trifluoroacetic acid mixtures, the adenine moiety of 3a is monoprotonated only at the N3 nitrogen up to acid concentrations of 50% by volume.

Fluorescent and colored trinitrophenylated analogs of ATP and GTP

“…2 and the section on Applications). Acidification of TNP‐ATP under mild conditions results in the opening of the dioxolane ring at the 2′‐oxygen to yield the 3′‐O‐TNP derivative as the only product [12].…”

“… Structures of TNP‐ATP and TNP‐GTP at neutral or basic pH values. At acidic pH, the opening of the dioxolane ring of TNP‐ribose moiety occurs at 2′‐oxygen to yield 3′‐ O ‐(2,4,6‐trinitrophenyl) derivative as the only product [12]. …”

Synthesis and Transformations of 2-Substituted Tetrahydro-4 H -benzo[4,5]thieno[2,3-d][1,3]oxazines and 2,3-Disubstituted Hexahydrobenzo[4,5]thieno[2,3-d]pyrimidines

“…The given structures of 15, 16, and 17 were established unequivocally by 1 H and 13 C-NMR. 13,15 The treatment of 3-aminothieno[2,3-d]pyrimidine 11 with aromatic aldehydes (4-methoxy, 2-hydroxy, 4-chloro and 4-bromobenzaldehyde) and isatin in refluxing ethanol afforded the aldimines 18a-d and 19, Downloaded by [University of Auckland Library] at 17:31 02 November 2014 SCHEME 4 respectively, in good yields. Instead peaks at δ 91.17-91.45 were observed, being assigned to the 1 -carbon atoms of the glycosyl amines 15-17.…”

L‐Erythruronic Acid Derivatives as Building Blocks for Nucleoside Analogs. Synthesis of 4′‐C‐Aryl‐D‐ribonucleosides

“…spectra of 24 indicated a predominant N-conformation6) (J(l',2')=4.2 Hz; J(3',4')=6 Hz) [25] and a slightly higher degree of puckering (J (2'. 3') = 6 Hz) then observed for adenosine [26]. In order to prepare the hydroxyphenyl nucleoside 29 (Scheme 3) the hemiacetal 26 was treated with diluted hydrochloric acid.…”

“…[23]. The conformational equilibrium of the furanose ring of 29 is shifted towards the S-conformation6) (J(1',2')=6 Hz; J(3',4')=4 Hz) [26]. The CD.…”