Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Kuijpers, W. H. A., Genderen, van, M. H. P., ... Buck, H. M. (1989). Synthesis of phosphate-methylated DNA fragments using 9-fluorenylmethoxycarbonyl as transient base protecting group. Journal of Organic Chemistry, 54(7), 1657-1664. DOI: 10.1021/jo00268a030 Link to publication Citation for published version (APA):General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Download date: 11. May. 2018 J. Org. Chem. 1989Chem. ,54, 1657Chem. -1664 1657Merck silica gel, 230-400 mesh, was used for flash chromatography, and Whatman Magnum-9 Partisil-10 and ODs-3 columns were used for preparative HPLC.Isolation and Extraction. Fresh leaves of C. dichogamus were collected in Kenya in mid-1987 (a voucher sample has been deposited a t the herbarium in the Botany Dept., UBC). The airdried leaves (225 g) were soaked in methanol (500 mL) overnight. The methanol extract was concentrated in vacuo to a gum, water was added, and the resulting suspension was exhaustively extracted with CH2C12. Evaporation of the combined organic extracts in vacuo gave a residue, which was fractionated via silica gel flash chromatography (step gradient: CH2C12 to EtOAc) to give crude crotoxides A (1) and B (2).Crotoxide A (1). The flash fractions containing crude crotoxide A (1) were combined and further purified by silica gel preparative TLC (2:l CH2C12/EtOAc). The preparative TLC fraction containing crotoxide A was dissolved in methanol (5 mL), palladium on charcoal was added (20 mg), and the suspension was stirred at room temperature under 1 atm of hydrogen for 2 days. Filtration of t...

A new synthesis route for long phosphate-methylated oligodeoxynucleotides is described, which were used as antisense inhibitors of the DNA replication. Phosphate-methylated oligomers hybridize more strongly with natural DNA than their natural analogues, due to the absence of electrostatic interstrand repulsions. Compared with phosphate-ethylated and methyl phosphonate systems, phosphate-methylated systems are preferable as antisense DNA, which was concluded from the high Tm values and sharp melting transitions of duplexes of phosphate-methylated and natural DNA. By using the Sanger dideoxy technique, it was shown that a complementary phosphate-methylated 18-mer can effectively and site-specifically block the DNA replication process at room temperature.

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The synthesis of the first dinucleotide with a pentacoordinated phosphorus as the internucleoside linkage is described. 31P-NMR measurements revealed that the phosphorus pseudorotation proceeds with rapid stereomutation.In the course of our investigations on con-

Abstract. The preparation and high-resolution 'H NMR conformational analysis of the two novel nucleoside analogues, 1-(3'-C-methyl-2'-deoxy-~-~-xylofuranosyl)urac~l (compound 1) and 9-(3'-C--methyl-2'-deoxy-f3-~-xylofuranosyl)adenine (compound 2), are described. Compounds 1 and 2 show a pronounced preference for the north conformation of the sugar ring. The north conformation corresponds with a sterically favoured equatorial location of the methyl group. The C4' -C5' conformation in 1 and 2 is predominantly y' (trans orientation of 0 5 ' and C3'). The configuration at C3' in 1 and 2 was corroborated via a one-dimensional NOE experiment. The structure of compound 1 (originally assigned as having the C3'-methyl group on the P-face of the furanosyl moiety) is revised on the basis of these data.