| Summary: | 碩士 === 中原大學 === 化學研究所 === 95 === The compound Rhamnolipid B, isolated from Pseudomonas
aeruginosa strain B5, is a glycolipid containing dirhamnose moiety. It
exhibits biological properties such as antibacterial, mycoplasmacidal,
antiviral activities, and an immunomodulator of autoimmune diseases.
Herein, we describe a facile, and efficient methodology for
synthesizing the rhamnolipid B to prepare its analogues to advance the
research and development of antibiotics.
All of the rhamnose building blocks in this research were prepared
from L- rhamnose, via one-pot two-step reaction, to afford glycosyl
acceptor Rha-1 (78%) and glycosyl donor Rha-2 (75%) in high yield,
respectively.
The synthesis of dirhamnose Rha-5 was proceeded by the
glycosylation of glycosyl acceptor Rha-1 with glycosyl donor Rha-2,
hydrolysation, per-O-acetylation, and chlorination in an overall yield of
49% over the four steps.
In this thesis we developed a facile, and efficient pathway for the
synthesis of the building block Mal-5 of β-hydroxydecanoic acid. The
optically active L-(-)-malic acid Mal-0 as starting material was through
the esterification, benzyloxymethylation, selective reduction, Wittig
reaction, and hydrogenation to give (R)-Methyl 3-hydroxydecanoate
Mal-5 in an overall yield of 20% over the five steps.
The final product Rha-6 was prepared from the glycosylation of the
dirhamnose Rha-5 with β-hydroxyester Mal-5 in 72%. The NOESY
spectrum of Rha-6 indicated that the stereochemistry of Mal-5 on
dirhamnose Rha-5 is α-configuration, namely the Mal-5 is at the axial
position.
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