The Chemodiversity of Purine as a Constituent of Natural Products

Abstract

In this review, I describe various natural manifestations of purine systems, i.e., methylated, higher-alkylated, and glycosylated forms. These comprise the purine alkaloids, cytokines, as well as the purine nucleoside antibiotics. In part, the compounds described herein were isolated from natural sources already long ago. However, some have been reported only during the last few years. The biological activities of most of the purine derivatives are briefly described, and, in some cases, syntheses are formulated. In particular, this article introduces the main synthetic principles for the generation of the purine ring system. The last chapter describes modern preparative routes for C-alkylation and C-arylation of purines.

Intermolecular Hydrogen Abstraction Reaction between Nitrogen Radicals in Purine Rings and Alkyl Ethers: A Highly Selective Method for the Synthesis of N‐9 Alkylated Purine Nucleoside Derivatives

“…[3] Alkylation is one of the commonly used methods for the synthesis of purine nucleoside derivatives. The most frequently used alkylating agents of purine bases are halogenated compounds, [4] mesylate, [5] and tosylate.…”

“…The solvent effects were examined and the results are shown in Table 1 (entries [1][2][3][4][5][6][7][8]. No reaction was observed in DMF, DMSO, DCM, and EtOAc (entries 1-4).…”

“…The reaction gave a low yield in cyclohexane presumably due to the poor solubility of the starting material (entry 5). A higher yield was obtained in CH 3 CN, but the result was still unsatisfactory (entry 6). THF, which is relatively inexpensive and easy to handle, was thus chosen as the solvent for further optimization, although 1,2-dichloroethane (DCE) could give the same result (entries 7 and 8).…”

Hoogsteen vs. Watson–Crick Base Pairing: Incorporation of 2‐Substituted Adenine‐ and 7‐Deazaadenine 2′‐Deoxy‐β‐D‐ribonucleosides into Oligonucleotides

“…2-Substituted adenine b-d-ribonucleosides have been discovered from natural sources [17]. These comprise isoguanosine (crotonoside; 1c) and its N(1)-Me derivative doridosine.…”

“…Another representative of this group of compounds is 2-methoxyadenosine (spongosine) which has been isolated also as its 2'-deoxy-b-d-ribonucleoside (1b). 2-Chloroadenine has been found as nucleobase of three nucleoside antibiotics, the ascamycins, as well as of trachycladine A [17]. Synthetic 2-chloro-2'-deoxyadenosine (cladribine, Cl 2 …”