An Efficient Synthesis of (R)-3-{(R)-3-[2-O-(α-L-Rhamnopyranosyl)- α-L-rhamnopyranosyl] oxydecanoyl}oxydecanoic Acid, a Rhamnolipid fromPseudomonas Aeruginosa

N-iodosuccinimide/triflic acid mediated one-pot two-step glycosylation of ethyl 2,3,4-tri-O-benzyl-1-thio-α-L-rhamnopyranoside (8) with phenyl 3,4-O-(2,3-dimethoxybutane-2,3-diyl)-1-thio-α-L-rhamnopyranoside (10b) and phenacyl (R)-3-hydroxydecanoate (13) gave rhamnolipid 17. The latter was transformed in five steps into the title compound 2. Esterification of 2 with diazomethane resulted into the corresponding methyl ester derivative 1.