Stereospecific syntheses of 3'-deuterated pyrimidine nucleosides and their site-specific incorporation into DNA

[reaction: see text] 2'-Deoxy-3'-deutero pyrimidines have been synthesized in high yields and incorporated into deoxyoligonucleotides using standard phosphoramidite chemistry. A key synthetic step is a stereospecific reduction of 3'-keto nucleosides using sodium triacetoxyborodeuteride to give 3'-deuterated thymidine and 2'-deoxy uridine nucleosides. Conversion of the corresponding phorphoramidites 7a and 7b to 4-triazolo derivatives has, for the first time, enabled incorporation of 2'-deoxy-3'-deutero cytidine and 2'-deoxy-3'-deutero-5-methyl cytidine into oligonucleotides.     

Thin-Layer Chromatography—Image Analysis Method for the Simultaneous Quantification of Andrographolide and Related Diterpenoids in Andrographis paniculata

JPC – Journal of Planar Chromatography – Modern TLC -     

Stability-Indicating TLC-Image Analysis Method for Quantification of Ceftriaxone Sodium in Pharmaceutical Dosage Forms

JPC – Journal of Planar Chromatography – Modern TLC - A simple and rapid thin-layer chromatographic (TLC)-image analysis method has been established for stability-indicating studies and...     

Unexpected formation of 2′-deoxy-N3-(3,3,3-trifluoro-1-propenyl)uridine via a Michael-type addition to 3,3,3-trifluoropropyne

Reaction of 3,3,3-trifluoropropyne with 2′-deoxy-5-iodouridine under conditions that have previously been used to prepare 5-alkynyl-2′-deoxyuridine derivatives gave 2′-deoxy-N3-(3,3,3-trifluoro-1-propenyl)uridine. This unexpected alkylation is a result of a Michael-type addition of N3 on the pyrimidine base to the electron deficient trifluoropropyne.     

Validated TLC-Image Analysis Method for Simultaneous Quantification of Curcuminoids in Curcuma longa

A simple and rapid thin layer chromatographic (TLC)-image analysis method was developed for simultaneous quantification of three curcuminoids; curcumin (CUR), desmethoxycurcumin (DES) and bisdesmethoxycurcumin (BIS), in Curcuma longa (turmeric). Chromatographic separation of the curcuminoids was achieved on silica gel 60 F254 TLC plates, using chloroform–hexane–methanol (1:1:0.1, v/v/v) as the mobile phase. Image analysis of the scanned TLC plate was performed by Photoshop 7.0 to quantify the amount of each curcuminoid. The method was validated and found to be accurate, reliable and convenient for the analysis of CUR, DES and BIS in turmeric.

     

Using solid-state 31P{19F} REDOR NMR to measure distances between a trifluoromethyl group and a phosphodiester in nucleic acids

REDOR is a solid-state NMR technique frequently applied to biological structure problems. Through incorporation of phosphorothioate groups in the nucleic acid backbone and mono-fluorinated nucleotides, 31P{19F} REDOR has been used to study the binding of DNA to drugs and RNA to proteins through the detection of internuclear distances as large as 13-14 A. In this work, 31P{19F} REDOR is further refined for use in nucleic acids by the combined use of selective placement of phosphorothioate groups and the introduction of nucleotides containing trifluoromethyl (-CF3) groups. To ascertain the REDOR-detectable distance limit between an unique phosphorous spin and a trifluoromethyl group and to assess interference from intermolecular couplings, a series of model compounds and DNA dodecamers were synthesized each containing a unique phosphorous label and trifluoromethyl group or a single 19F nucleus. The dipolar coupling constants of the various 31P and 19F or -CF3 containing compounds were compared using experimental and theoretical dephasing curves involving several models for intermolecular interactions.