Abstract
As a major component of outer layer of gram-negative bacteria, glycoconjugate of L-rhamnose plays a crucial role in mediating cell-cell recognition. The desired glycoceramide analog (2S,3R,4S,5R,6R)-2-((2R, 3R,4R,5S,6S)-2-((2S,3S,4R)-2-amino-3,4-dihydroxyoctadecyloxy)-3,5-dihydroxy-6-methyltetrahydro-2H-pyran-4-yloxy)-6-(aminomethyl)tetrahydro-2H-pyran-3,4,5-triol was prepared from commercial L-rhamnose and phytosphingosine via intermediate: (2R,4S,5S,6S)-2-(azidomethyl)-6- ((2S,3S,4R,5R,6S)-3-(benzoyloxy)-5-(4-methoxybenzoyloxy)-2-methyl-6-(p-tolylthio)tetrahydro-2H-pyran-4-yloxy)tetrahydro-2H-pyran-3,4,5-triyl tribenzoate (yield : 17% base on rhamnose) and intermediate: (2S,3S,4R)- 2-azido-1-hydroxyoctadecane-3,4-diyldibenzoate (yield : 44% base on phytosphingosine) in a total yield of 5%. Radiolabeled glycoceramides were attempted to be prepared for imiaging purpose. Rhamnosyl phytosphingosine labeled with 18F emerged as our target compound. The precursor to 18F rhamnosyl phytosphingosine analogs e.g. a tosylate was thus prepared. An alcohol required for tosylate preparation, (2R,3R,4R, 6S)-2-((2S,3S,4R)-2-azido-3,4-bis(tert-butyldimethylsilyloxy)octa decyloxy)-5-(benzoyloxy)-4-(2-chloroacetoxy)-6-methyltetrahydro-2H- pyran-3-yl 4-methoxybenzoate, was obtained via a 11-step synthesis starting from rhamnose in total 13% yield.