Highly diastereoselective allylation of lactols and their ethers using molecular iodine

Ene Reaction of Nitrosocarbonyl Mesitylene with the Cinnamyl Alcohol: Metabolic Activity and Apoptosis of the Synthetized 6-Chloropurine N,O-Nucleoside Analogues

“…The stereochemical outcome is in full accordance with Yadav’s and Woerpel’s observations on the behavior of oxocarbenium ions, simply alkyl or aryl substituted. 12 Table 1 reports the yields, physical–chemical data, and the relevant 1 H NMR spectroscopic data supporting the structural assignments given in Scheme 3 . Compounds 6a–d were fully characterized, and their structures correctly attributed to the cis- or trans-series; these labels refer to the stereochemical relationship between the phenyl group and the purine ring located on the isoxazolidine moiety.…”

Highly Stereoselective Glycosylation Reactions of Furanoside Derivatives via Rhenium (V) Catalysis

“…Relative stereochemistry of 12 has been established by chemical correlation with the known Borhan allylated diol, previously reported as diol 4 . 12 This complete selectivity is remarkable in light of the fact that other catalytic approaches 3 afford the corresponding TBS-protected 12 in 90:10 selectivity. Indeed, in order to achieve the same level of stereoselectivity, the reaction requires an equimolar amount of Lewis acids such as BF 3 etherate 13 or SnBr 4 .…”

“…The latter was obtained with a 1,3- syn stereoselectivity of 95:5, a remarkable result in light of the poor selectivity obtained by Yadav for an analogous compound. 3 The use of 2-(trimethylsilyl)-2,3-pentadiene afforded product 16 , with a pendant alkyne, in good yield and high 1,3- syn stereoselectivity and 7:3 (UPLC analysis) at a C-4′ ( S )-stereocenter. 16 Noncarbon-based nucleophiles such as nitrogen (Me 3 SiN 3 ), sulfur (Me 3 SiSPh), and hydride (Et 3 SiH) 17 afforded the corresponding azido- ( 17 ) and thio- ( 19 ) glycosides and 1,4-anhydro-2-deoxy-glycitol ( 18 ) in high yield and good selectivity.…”

“…In 2009, Yadav reported a protocol using molecular iodine in CH 2 Cl 2 at cryogenic temperatures. 3 In the same year, Fiestad delivered an alternative approach to solve the innate stereochemical problems of cyclic, five-membered oxocarbenium ions, developing an allylation reaction on a 2,7-dioxabicyclo[2.2.1]heptane ring system which uses a catalytic amount of TiCl 4 as a Lewis acid. 4 As a part of our program aimed to explore the chemistry of rhenium (V), 5 herein, we report a new talent of oxo–rhenium complex 8 , namely, its ability to promote the formation of an oxocarbenium species in a catalytic fashion ( Scheme 2 ).…”

Applications of Wittig Reaction in the Total Synthesis of Natural Macrolides

“…[127,128] Remarkably, they are active antifungal agents and active inhibitors of ergosterol synthesis. [129] A stereoselective total synthesis of 13-membered macrocycle PF1163 A, an antifungal agent, was achieved starting from D-xylose. This method includes a diastereoselective allylation of lactal ether, [130] reductive ring opening of tetrahydrofuran ring, [131] enantioselective methylation reaction, Yamaguchi esterification, and also ring closing metathesis as key steps.…”