- Synthesis of α-l-rhamnosyl ceramide and evaluation of its binding with anti-rhamnose antibodies
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An α-l-rhamnosyl ceramide (1, α-l-RhaCer) has been prepared that was recognized by anti-l-rhamnose (anti-Rha) antibodies. During these studies we explored the use of an α-l-rhamnosyl thioglycoside and a trichloroacetimidate as a glycosyl donors. Subsequently, the acceptors desired for glycosylation, 3-O-benzoylazidosphingosine or 3-O-alloxycarbonylsphingosine, were prepared from d-xylose. The thioglycoside donor, 2,3,4-tri-O-acetyl-1-(4-tolyl)thio-α-l-rhamnopyranoside, and the trichloroacetimidate donor, 2,3,4-tri-O-acetyl-1-(2,2,2-trichloroethanimidate)-α-l-rhamnopyranoside, were synthesized in 50% and 78% yield overall, respectively. The synthesis of the glycosylation acceptor employed an addition-fragmentation olefination that was successfully carried out in 53% yield. With the successful synthesis of key intermediates, α-l-RhaCer (1) was prepared without any insurmountable obstacles. Anti-Rha antibodies were prepared in BALB/c mice by immunizing them with rhamnose-ovalbumin (Rha-Ova) with Sigma Adjuvant System (SAS) and the anti-l-Rha antibodies were isolated from the blood sera. Liposomes and EL4 tumor cells were used as model systems to demonstrate the ability of 1 to insert into a lipid bilayer. The interaction of the liposomes or the EL4 cells with α-l-RhaCer (1) and anti-Rha antibodies were investigated by fluorescence microscopy and flow cytometry, respectively, to confirm the ability of glycolipid 1 to be displayed on the tumor cell surface as well as the ability to be recognized by anti-Rha antibodies.
- Long, David E.,Karmakar, Partha,Wall, Katherine A.,Sucheck, Steven J.
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- Synthesis of unusual amino acids: N-(tert-butoxycarbonyl)-L-vinyl glycine and N-(tert-butoxycarbonyl)-L-homophenylalanine
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The synthesis of the unusual amino acids N-(tert-butoxycarbonyl)-L-vinyl glycine and N-(tert-butoxycarbonyl)-L-homophenylalanine starting from commercially available D-xylose via an alkylative fragmentation method is described.
- Chandrasekhar,Raza, Abbas,Takhi, Mohamed
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p. 423 - 428
(2007/10/03)
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- An efficient stereoselective synthesis of sphingosine
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A stereocontrolled synthesis of D-(+)-erythro-sphingosine (1), starting from D-xylose as chiral pool material and employing the addition-fragmentation reaction of tosyl hydrazone of 2,3:4,5-di-O-isopropylidene-D-xylose as a key step for the chain extension with concomitant trans-selective C=C bond formation, is described.
- Kumar, Pradeep,Schmidt, Richard R.
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- An expeditious approach for the synthesis of optically active allyl alcohols
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Aldehyde tosylhydrazones having an adjacent O-isopropylidene group undergo a condensation-fragmentation process in the presence of alkyl magnesium and alkyllithium reagents to yield chiral allyl alcohols.
- Chandrasekhar,Takhi,Yadav
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p. 5071 - 5074
(2007/10/02)
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