Showing papers by "Daniel M. Brown published in 1999"

A Dimroth rearrangement of pyrimidine nucleosides

Abstract: N 4-Acylamino-2′-deoxycytidine derivatives, 4a–c, undergo acid-promoted cyclisation to give [1,2,4]triazolo[4,3-c]pyrimidin-5(6H)-ones, 5a–c, in the presence of pyridinium chloride. This reaction has been demonstrated for a series of analogues. Treatment of the cyclised products in basic media gives rise to a novel Dimroth-type rearrangement leading to [1,2,4]triazolo[1,5-c]pyrimidin-5(6H)-ones, 7a–c. The crystal structure of one such product, 15, was confirmed by X-ray analysis.

5′-Tailed Octanucleotide Primers for Cycle Sequencing

Abstract: Recently we reported the use of octamer primers tailed with 5-nitroindole for use as primers in cycle sequencing reactions. Here we report the successful use of some other universal base analogues to improve the effectiveness of an octamer sequencing primer. These analogues are 5-nitroindazole, 3-nitropyrrole and benzimidazole.

The Synthesis of Bicyclic N4‐Amino‐2′‐deoxycytidine Derivatives

Abstract: Nucleosides which have ambivalent tautomeric properties have value in a variety of nucleic acid hybridization applications, and as mutagenic agents. We describe here synthetic studies directed to stable derivatives of this kind of nucleoside based on N4-aminocytosine. Treatment of the 4-(1H-1,2,4-triazol-1-yl)-5-(chloroethyl)pyrimidinone nucleoside derivative 5 with hydrazine leads to formation of the 6,6-bicyclic pyrimido-pyridazin-7-one 3, and with methylhydrazine to the corresponding fixed tautomeric 1-methyl derivative 7 (Scheme 1). If these cyclization reactions are carried out in the presence of a base, the 6-ring bicyclic derivatives undergo rearrangement to their corresponding 5-ring pyrrolo-pyrimidin-2-one analogues 8 (Scheme 2). In the reaction of the triazolyl derivative 5 with 1-[(benzyloxy)carbonyl]-1-methylhydrazine, spontaneous cyclization gives the 5-ring derivative 13 related to 8 rather than the open-chain product 12 (Scheme 4). Reaction of an acetylated analogue of triazolyl derivative 5 with 1,1-dimethylhydrazine gives rise to some of the open-chain product 9, but it too cyclizes to a product that we have assigned the structure of the 6,6-ring quaternary ammonium salt 11 (Scheme 3).

Synthesis and Polymerase Incorporation Properties of a Tricyclic Pyrrolopyrimidine Related to N6-Hydroxy-2′-deoxyadenosine

Abstract: The tricyclic nucleotide dLTP has been synthesised. It is incorporated into DNA using a variety of polymerases opposite both template T and dC in vitro and in vivo.

Random Mutagenesis Using 2-Amino-9-(2-Deoxy-β-D-Ribofuranosyl)Purine-5′-Triphosphate and the Polymerase Chain Reaction

Abstract: Base analogues offer an attractive method for mutagenising DNA in combination with the polymerase chain reaction (PCR). We have synthesised the 5′-triphosphate-2′-deoxyribosyl derivative of 2-aminopurine (dAPTP), one of the first base analogues to be used for mutagenesis, and examined its utility in PCRs. An E. coli amber suppressor gene, supF, was used as a template for mutagenesis. The analogue induced exclusively transition mutations, but at a low frequency, consistent with its weak mutagenicity in vivo.

A Dimroth Rearrangement of Pyrimidine Nucleosides.

Abstract: N 4-Acylamino-2′-deoxycytidine derivatives, 4a–c, undergo acid-promoted cyclisation to give [1,2,4]triazolo[4,3-c]pyrimidin-5(6H)-ones, 5a–c, in the presence of pyridinium chloride. This reaction has been demonstrated for a series of analogues. Treatment of the cyclised products in basic media gives rise to a novel Dimroth-type rearrangement leading to [1,2,4]triazolo[1,5-c]pyrimidin-5(6H)-ones, 7a–c. The crystal structure of one such product, 15, was confirmed by X-ray analysis.

Synthesis and Polymerase Incorporation Properties of a Tricyclic Pyrrolopyrimidine Related to N6‐Hydroxy‐2′‐deoxyadenosine

Abstract: The tricyclic nucleotide dLTP has been synthesised. It is incorporated into DNA using a variety of polymerases opposite both template T and dC in vitro and in vivo.