Home About us Contact
|
Home About us Contact | ||
|
|
||
Terminal Triple Bond (terminal + triple_bond)
Selected AbstractsDNA Containing Side Chains with Terminal Triple Bonds: Base-Pair Stability and Functionalization of Alkynylated Pyrimidines and 7-DeazapurinesCHEMISTRY & BIODIVERSITY, Issue 5 2006Frank Seela Abstract The synthesis of a series of oligonucleotides containing 5-substituted pyrimidines as well as 7-substituted 7-deazapurines bearing diyne groups with terminal triple bonds is reported. The modified nucleosides were prepared from the corresponding iodo nucleosides and diynes by the Sonogashira cross-coupling reaction. They were converted into phosphoramidites and employed in solid-phase synthesis of oligonucleotides. The effect of the diyne modifications on the duplex stability was investigated. The modified nucleosides were used for further functionalization using the protocol of Huisgen,Sharpless [2+3] cycloaddition (,click chemistry'). [source] Synthesis of the Salicylihalamide Core Structure from Epichlorohydrin, Laying the Foundation to Macrolactone CollectionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2005Christian Herb Abstract Starting from (R)-epichlorohydrin, two successive carbon,carbon bond formations, one with acetylide and the other with cyanide, led to the 3-hydroxynitrile 20. This compound was further elaborated to the enynol 29 via an Evans aldol reaction of the derived aldehyde 22 with the pentenoyloxazolidinone 23 and conversion of the carboxyl to a methyl group after the aldol reaction. Mitsunobu esterification of the enynol 29 with the benzoic acid 5 gave rise to the ester 30 with two double bonds and one triple bond. After protection of the terminal triple bond with a TIPS group, the ring closing metathesis proceeded in good yield. The macrolactone E -33 was converted into the vinyl iodide 34 and the pyridin containing salicylihalamide analog 36. The described sequence, the two-sided elongation of epichlorohydrin appears as a general route to secondary alcohols that can be further elaborated to functionalized macrolactones. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Thiophenol-Mediated 1,5-Hydrogen Atom Abstraction: Easy Access to Mono- and Bicyclic CompoundsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-13 2005Florent Beaufils Abstract A thiophenol-mediated method for cyclization of alkynes is described. The reaction cascade involves the intermolecular addition of a phenylthiyl radical to a terminal triple bond generating an alkenyl radical, followed by a 1,5-hydrogen atom transfer and a 5- exo- trig radical cyclization. This very efficient tin-free procedure allows one to prepare highly functionalized cyclopentane derivatives as well as fused bicyclic and spirocyclic compounds from easily available precursors. During this cyclization process, a phenylthio moiety is incorporated into the final cyclized products. This functionalization is particularly attractive for further transformation of the products. [source] DNA Containing Side Chains with Terminal Triple Bonds: Base-Pair Stability and Functionalization of Alkynylated Pyrimidines and 7-DeazapurinesCHEMISTRY & BIODIVERSITY, Issue 5 2006Frank Seela Abstract The synthesis of a series of oligonucleotides containing 5-substituted pyrimidines as well as 7-substituted 7-deazapurines bearing diyne groups with terminal triple bonds is reported. The modified nucleosides were prepared from the corresponding iodo nucleosides and diynes by the Sonogashira cross-coupling reaction. They were converted into phosphoramidites and employed in solid-phase synthesis of oligonucleotides. The effect of the diyne modifications on the duplex stability was investigated. The modified nucleosides were used for further functionalization using the protocol of Huisgen,Sharpless [2+3] cycloaddition (,click chemistry'). [source] | ||||||||||