61490-70-8Relevant academic research and scientific papers
Synthesis of (2 S,3 R,5 R)-2-Azido-3,5-dihydroxynonadecane Sphingolipid Analogue
Pemha, René,Pegnyemb, Dieudonné Emmanuel,Mosset, Paul
, p. 2572 - 2578 (2020)
A concise and highly efficient synthesis of an enigmol analogue has been achieved. The synthetic strategy features Jacobsen's hydrolytic kinetic resolution (HKR) and epoxide opening by alkynyl boranes as the key steps.
Synthesis of immunostimulatory α- C -galactosylceramide glycolipids via sonogashira coupling, asymmetric epoxidation, and trichloroacetimidate- mediated epoxide opening
Liu, Zheng,Byun, Hoe-Sup,Bittman, Robert
scheme or table, p. 2974 - 2977 (2010/11/16)
Stereocontrolled syntheses of α-C-GalCer (2) and its α-C-acetylenic analogue 6 were accomplished in high efficiency by a convergent construction strategy from 1-hexadecene and d-galactose. The key transformations include Sonogashira coupling, Sharpless asymmetric epoxidation, and Et2AlCl-catalyzed cyclization of an epoxytrichloroacetimidate to generate protected dihydrooxazine 21.
Methanesulfonamide: A cosolvent and a general acid catalyst in sharpless asymmetric dihydroxylations
Junttila, Mikko H.,Hormi, Osmo O.E.
experimental part, p. 3038 - 3047 (2009/08/08)
To obtain information about the effect that methanesulfonamide has in the hydrolysis step in Sharpless asymmetric dihydroxylation, a series of aliphatic and conjugated aromatic olefins were dihydroxylated with and without methanesulfonamide. The hypothesis in this study was that methanesulfonamide is a cosolvent that aids in the transfer of the hydroxide ions from the water phase to the organic phase. A plot of t90% versus the computational partition coefficient clog P of the intermediate osmate ester of nonterminal aliphatic olefins revealed that the polarity of the intermediate osmate ester has a significant effect on the reaction time and methanesulfonamide effect. The more polar the intermediate osmate ester, the faster is the reaction without methanesulfonamide and the smaller the accelerating methanesulfonamide effect. Methanesulfonamide had no accelerating effect in the asymmetric dihydroxylation of short chain terminal aliphatic olefins as a result of easier accessibility of terminal osmate ester groups to the water phase. A cosolvent hypothesis was found not to be valid in asymmetric dihydroxylations of conjugated aromatic olefins. In the reaction conditions used in Sharpless asymmetric dihydroxylation, weakly acidic methanesulfonamide was found to be a general acid catalyst that protonates the intermediate osmate esters of conjugated aromatic olefins in the hydrolysis step.
Sodium chlorite as an efficient oxidant and hydroxy ion pump in osmium-catalyzed asymmetric dihydroxylation
Junttila, Mikko H.,Hormi, Osmo E. O.
, p. 4816 - 4820 (2007/10/03)
Sodium chlorite is an efficient stoichiometric oxidant in Sharpless asymmetric dihydroxylation. One sodium chlorite provides the reaction with the stoichiometric number of electrons and hydroxide ions needed to dihydroxylate two olefins without the consumption of any additional base. 100% conversion in sodium chlorite asymmetric dihydroxylation of styrene was achieved twice as fast as in the established Sharpless K3[Fe(CN)6] dihydroxylation. Even internal olefins were dihydroxylated fast with sodium chlorite without hydrolysis aids. Eight olefins were dihydroxylated to corresponding vicinal diols with yields and ees as good as those reported in the literature for other similar processes.
Syntheses and interfacial behaviour of neoglycolipid analogues of glycosyl ceramides
Lafont, Dominique,Bouchu, Marie-Noelle,Girard-Egrot, Agnes,Boullanger, Paul
, p. 181 - 194 (2007/10/03)
Four glycosyl ceramides analogues having D-galactose or 2-acetamido-2-deoxy-D-glucose moieties linked to enantiomeric lipids have been synthesised to study their interfacial behaviour at the air | water interface. The lipid chains were prepared in two steps by opening 1,2-epoxyhexadecane using Jacobsen kinetic hydrolytic resolution (KHR) followed by an azidosilylation reaction of the diol so obtained. Glycosylation reactions were realised either with 2,3,4,6-tetra-O-benzoyl-α-D-galactopyranosyl trichloroacetimidate or 1,3,4,6-tetra-O-acetyl-2-allyloxycarbonylamino-2-deoxy-β-D-glucopyranose as donors and (2R)- or (2S)-2-azidohexadecanol derivatives as acceptors. Transformation of the azido glycosides into N-acylated products was done by a modified Staudinger reaction in the presence of fatty acyl chlorides. The four neoglycolipids are able to form a condensed monolayer at the air | water interface; their π-A isotherm diagrams are similar to that described for the natural glycosyl ceramides. The detailed analysis of the isotherms, taking into account the chirality of the lipid chains, allowed to determine the contribution of the different parts of the molecule under the monolayer packing.
A new approach to the stereoselective total synthesis of isotopically labeled D-ribo-phytosphingosine
Li, Shengrong,Pang, Jihai,Wilson, William K.,Schroepfer Jr., George J.
, p. 1697 - 1707 (2007/10/03)
We describe a novel stereoselective total synthesis of D-ribo-[1,1-2H- 1,2-13C]phytosphingosine (12). Chirality at the incipient C-4 position was derived from asymmetric dihydroxylation of 1-hexadecene. The remaining chiral centers were formed by Sharpless epoxidation of an allylic alcohol, followed by benzoylcarbamate cyclization to furnish a 2-amino-1,3,4-triol derivative with the desired stereochemistry. The 2H and 13C labels were introduced by Horner-Emmons condensation of 13C-labeled triethyl phosphonoacetate, followed by reduction of the resulting carboxylic ester with AlCl3/LiAlD4. Mass spectral results indicated the suitability of 12 as an internal standard for analyses by the isotope dilution method.
