A new RNA synthetic method with a 2'-O-(2-cyanoethoxymethyl) protecting group

A novel method for the synthesis of RNA oligomers with 2-cyanoethoxymethyl (CEM) as the 2'-hydroxyl protecting group has been developed. The new method allows the synthesis of oligoribonucleotides with an efficiency and final purity comparable to that obtained in DNA synthesis. [structure: see text]     

'Thiacalix[4]aniline' as a highly specific extractant for Au(III) and Pd(II) ions

Thiacalix[4]aniline (4), a cyclic tetramer of p-tert-butylaniline bridged with four sulfides, extracted Au(III) and Pd(II) ions specifically from acidic solutions among 41 metal ions including soft metal ions such as Hg(II), Cd(II), Zn(II), Pb(II), and Cu(II).     

A synthesis of 11-homo-aldosterone

A synthesis of 11-homo-aldosterone acetate (1a) is described. 3β-Acetoxy-11-methylene-5α,25D-spirostan (3) was converted in 4 steps into 3β-acetoxy-11β-acetoxymethyl-5α-pregnan-20-one (9, Chart I), which was photocyclized to 20a, saponified regioselectively, and oxidized to 3-oxo-11β-acetoxymethyl-18,20-cyclopregnan-20α-ol-3-one (22, Chart II). Introduction of the 1,4-diene in 22 followed by a selective reduction of the 1-ene afforded 11β-acetoxymethyl-18,20-cyclopregn-4-en-20α-ol-3-one (26). Finally, the 18,20-cyclo ring of 26 was manipulated through 30, 31, 32, 33 to produce 1a. The bulky 11β-acetoxymethyl group distorted the steroid molecule to such an extent that the routine photochemical functionalization of the angular Me-18 via a nitrite or a hypoiodite became inoperative, and routine procedures for introduction of a 4-ene into 5α-3-one via a 1,4-dien-3-one were unsuccessful. Two new methods for the introduction of a 4-ene into steroidal 5α-3-ones were investigated using 5α-cholestanone and 5α-dihydrotestosterone as models. The first route, which was applicable to the synthesis of 1a, was the stepwise introduction of a 1-ene and a 4-ene utilizing Sharpless's acidic phenylselenyl chloride procedure, followed by a selective reduction of the 1-ene. The second route, which appeared equally promising, was protection of the C-2 site with N-methylanilinomethylene followed by introduction of the 4-ene and subsequent deprotection of the C-2.     

Precolumn derivatization reagents for high‐speed analysis of amines and amino acids in biological fluid using liquid chromatography/electrospray ionization tandem mass spectrometry

A rapid analytical method for amines and amino acids was developed, involving derivatization with the novel reagent 3‐aminopyridyl‐N‐hydroxysuccinimidyl carbamate (APDS), followed by reversed‐phase high‐performance liquid chromatography and electrospray ionization tandem mass spectrometry (HPLC/ESI‐MS/MS). More than 100 different analytes with amino groups, including amino acids in biological fluids such as mammalian plasma, could be measured within 10 min. The analytes were easily derivatized with APDS under the mild conditions. Selective reaction monitoring of ESI‐MS/MS in positive mode was carried out to include the transitions of all of the protonated molecular ions of analytes derivatized with APDS to the common fragment at m/z 121, which was derived from the amino pyridyl moiety of the reagent. We evaluated the retention time precision, the quantification limits, the linearity, the intra‐ and inter‐day precisions and the accuracy of 22 typical amino acids found in biological fluids, by analyzing a standard amino acid mixture and rat plasma. The intra‐day relative standard deviations (RSDs) of the retention times of the 22 amino acids and their internal standards were within 0.9% and the inter‐day RSDs were less than 1.1%, except for asparagines, with an RSD of 1.9%. The intra‐day and inter‐day RSDs of amino acid analyses in rat plasma were within 8.0% and 4.5%, respectively. The method, which facilitates the amino acid analysis of more than 100 samples in a day, represents an alternative to traditional amino acid analysis techniques, such as chromatography using postcolumn derivatization by ninhydrin. Copyright © 2009 John Wiley & Sons, Ltd.