Some pteridines having various kind of sugars attached to the hydroxyalkyl side-chain at C-6 are known to occur in certain prokaryotes. As for a glycoside of biopterin (1), 2'-O-(α-D-glucopyranosyl)biopterin (2) was isolated from various kinds of cyanobacteria . We have undertaken a synthetic exploration of various types of natural pterin glycosides owing to a marked interest in their physiological functions and biological activities as well as the structural proof of those natural products . We present here the first sythesis of microcystbiopterin B (3), which was isolated from Microcystis spp. bloom biomass  (Scheme 1).
The key, versatile precursor N²-(N,N-dimethylaminomethylene)-1’-O-PMB-3-NPE-biopterin (8) was efficiently prepared from the D-xylofuranose derivative (4) via 5–7 in 11 steps involving condensation of the phenylhydrazone (6) with 2,4,5-triamino-6-hydroxypyrimidine. Meanwhile, the glycosyl donor 2-O-PMB-3-O-methyl-α-D-glucopyranosyl bromide (9) was prepared from D-glucose in 11 steps. Glycosylation of 8 with 9 in the presence of silver triflate and tetramethylurea predominantly afforded the corresponding α-D-glucopyranoside (10). The first synthesis of microcystbiopterin B (3) was achieved by successive removal of the protecting groups of 10.
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