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2005
Nucleic acids
U 0700
Modified Tricyclic Analogues of Acyclovir. A Direct Alkynylation in the Fused
— Two types of 7-alkynylated analogues are prepared. Products which are
06- 187 Ring.
unsubstituted at N-5 are exceptionally unstable whereas the presence of a permanent
N-5 substituent sufficiently decreases the reactivity of the triple bond of alkynylated
analogues. The permanent substitution at N-5 is achieved with a hydroxypropyl group,
cf. (III), which is acetylated to avoid side reactions. Iodination and subsequent alkynylation of 6-unsubstituted and 6-methyl substituted compounds (VI) indicate substantial differences in their reactivity. The lower reactivity of (VIa) is the reason for an
undesired double course of its coupling reaction, cf. (VIa)→(VIII)+(Va). Thus, to
install the tricyclic system, four steps are required: i) N-5 protection, ii) iodination in
position 7, iii) Sonogashira coupling with an alkyne, and iv) deprotection. —
(ZEIDLER, J.; Collect. Czech. Chem. Commun. 69 (2004) 8, 1610-1630; Inst.
Bioorg. Chem., Pol. Acad. Sci., PL-61-704 Poznan, Pol.; Eng.) — H. Hoennerscheid
2005
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