929682-84-8Relevant academic research and scientific papers
Copper(II)-catalyzed silylation of activated alkynes in water: Diastereodivergent access to E- or Z-β-silyl-α,β-unsaturated carbonyl and carboxyl compounds
Calderone, Joseph A.,Santos, Webster L.
supporting information, p. 4154 - 4158 (2014/05/06)
Copper(II)-catalyzed silylation of substituted alkynylcarbonyl compounds was investigated. Through the activation of Me2PhSiBpin in water at room temperature and open atmosphere, vinylsilanes conjugated to carbonyl groups are synthesized in high yield. A surprising diastereodivergent access to olefin geometry was discovered using a silyl conjugate addition strategy: aldehydes and ketones were Z selective while esters and amides were exclusively transformed into the E products. Dial a diastereomer: The title reaction proceeds through the activation of Me2PhSiBpin in water at room temperature and open atmosphere to produce high yields of vinylsilanes conjugated to carbonyl groups. A surprising diastereodivergent access to olefin geometry was discovered using this silyl conjugate addition strategy: aldehydes were Z selective while esters and amides exclusively delivered the E-configured products.
Total synthesis and biological evaluation of the cytotoxic resin glycosides ipomoeassin A-F and analogues
Nagano, Takashi,Pospisil, Jiri,Chollet, Guillaume,Schulthoff, Saskia,Hickmann, Volker,Moulin, Emilie,Herrmann, Jennifer,Mueller, Rolf,Fuerstner, Alois
supporting information; experimental part, p. 9697 - 9706 (2010/04/29)
A multitasking C-silylation strategy using the readily available compound 26 as a surrogate for cinnamic acid represents the key design element of a total synthesis of all known members of the ipomoeassin family of resin glyosides. This protecting group maneuver allows the unsaturated acids decorating the glucose subunit of the targets to be attached at an early phase of the synthesis, prevents their participation in the ruthenium-catalyzed ring-closing metathesis (RCM) used to form the macrocyclic ring, and protects them against reduc tion during the hydrogenation of the resulting cycloalkene over Wilkinson's catalyst. As the C-silyl group can be concomitantly removed with the O-TBS substituent using tris(dimethylamino)sulfonium difluorotrimethylsilicate (TASF) in acetonitrile, no separate protecting group manipulations were necessary in the final stages, thus contributing to a favorable overall "economy of steps". In addition to the naturally occurring ipomoeassins, a small set of synthetic analogues has also been prepared by "diverted total synthesis". The cytotoxicity of these compounds was assayed with two different cancer cell lines. The recorded data confirm previous findings that the acylation- and oxygenation pattern of these amphiphilic glycoconjugates is highly correlated with their biological activity profile. Ipomoeassin F turned out to be the most promising member of the series, showing IC50 values in the low nanomolar range.
Total syntheses of ipomoeassin B and E
Fuerstner, Alois,Nagano, Takashi
, p. 1906 - 1907 (2007/10/03)
A concise, flexible, and efficient total synthesis of the cytotoxic resin glycosides ipomoeassin B (1) and ipomoeassin E (2) is reported which features the advantages of a novel protecting group strategy employing (Z)-3-dimethyl(phenyl)silyl-2-propenoic acid as cinnamic acid surrogate. The use of this readily available compound allowed the macrocycle of the glycolipids to be formed by ring closing olefin metathesis (RCM) with the aid of the second generation Grubbs carbene complex 12. The resulting E/Z mixture could be selectively hydrogenated using Wilkinson's catalyst [RhCl(PPh3)3] without affecting the unsaturated esters in the periphery of the compound, before the C-silyl group was cleaved off with TASF [tris(dimethylamino)sulfonium difluorotrimethylsilicate] under notably mild conditions to release the required cinnamate moiety. Other key steps of the synthesis route comprise the formation of the disaccharide linkage by the trichloroacetimidate method, the formation of the chiral acid segment 19 via a VO(acac)2-catalyzed, tert-BuOOH-induced oxidative rearrangement of the optically pure furyl alcohol (-)-15 (Achmatowicz-type reaction), and a reductive cleavage of the 4,6-O-p-methoxybenzylidene acetal in 5 with NaBH3CN and Me3SiCl (TMSCl), the regiochemical course of which was found to be opposite to that previously reported in the literature for sterically less encumbered substrates. Copyright
