32313-86-3Relevant academic research and scientific papers
Novel photoacid generators for photodirected oligonucleotide synthesis
Serafinowski, Pawel J.,Garland, Peter B.
, p. 962 - 965 (2007/10/03)
Photodirected oligonucleotide synthesis uses either direct or indirect light-dependent 5′-deprotection. Both have been reported to give lower stepwise synthetic yields than conventional methods. The deficiency appears to be due to incomplete deprotection at the oligonucleotide 5′-position and, additionally in the case where photodirection is indirect and uses photogenerated photoacid to effect 5′-detritylation, the depurinating effects of strong acid. We have developed novel photosensitive-2-nitrobenzyl esters that on irradiation with near UV light generate α-chloro-substituted acetic acids, such as trichloroacetic acid, which are widely and successfully used in conventional solid-phase oligonucleotide synthesis. α-Phenyl-4,5-dimethoxy-2-nitrobenzyltrichloroacetate and α-phenyl-4,5-dimethoxy-2,6-dinitrobenzyltrichloroacetate showed appropriate photochemical characteristics and were used for photodirected synthesis of a variety of oligonucleotides, including (T)5, TATAT, TGTGT, (T)10, (AT)5, (CT)5 (GT)5 and (TGCAT)2 on a modified Millipore Expedite DNA synthesizer. The outcomes were compared with those obtained by use of directly added trichloroacetic acid (conventional synthesis). The stepwise yields for the two methods were essentially identical.
Stereoselective Construction of 22-Oxygenated Steroid Side Chains by Dimethylaluminum Chloride-Mediated Ene Reactions of Aldehydes
Houston, Todd A.,Tanaka, Yoshio,Koreeda, Masato
, p. 4287 - 4292 (2007/10/02)
Dimethylaluminum chloride-mediated ene reactions of aldehydes with (Z)-3β-acetoxy-5,17(20)-pregnadiene (3) at low temperatures followed by acetylation of the resulting alcohols have been shown to produce stereoselectively 22-acetoxylated steroid derivatives in good to excellent yields.Interestingly, the stereochemical outcome of these ene reactions has been found to be dependent upon the size of the aldehyde employed; the less sterically demanding aldehydes such as 4-methylpentanal and cyclohexanecarboxaldehyde afford the (20α,22α)-22-acetoxy products (4a) stereoselectively, whereas the relatively congested aldehydes such as benzaldehyde and other aromatic aldehydes produce predominantly the (20α,22β)-22-acetates (4b).This novel stereochemical observation has been rationalized in terms of the relative stabilities of the two most plausible transition states where the difference in the relative bulk between the R group of the aldehyde RCHO and the Me2AlCl coordinating to the aldehyde oxygen in an anti-fashion seems to be manifested in the stereochemical outcome at C-22 of the ene products.
