Glucosamine donors 1â3 having N-TCP,
N,N-diacetyl and N-Teoc protection,
respectively, give with
Nα-Boc-protected serine and threonine
benzyl esters 4a,b as acceptors exclusively the
β-glycosides; they can be transformed into
O-GlcNAc serine and threonine derivatives 8a,b. The high
yielding O-glycosylation of compounds 4a,b with trichloroacetimidate 3
and the ease of replacement of the N-Teoc group by the
N-acetyl group prompted the use of
Nα-Fmoc-protected serine and
threonine allyl (9a,b) and Pfp active esters (12a,b) as acceptors, thus
very efficiently yielding the corresponding
O-(N,O-acetylglucosamino) serine and
threonine derivatives 11a,b and 14a,b as active esters.
分别具有 N-
TCP、N,N-二乙酰基和 N-Teoc 保护的
葡萄糖胺供体 1â3 与 Nα-Boc 保护的
丝氨酸和苏
氨酸苄酯 4a,b 一起作为δ-糖苷的受体;它们可以转化为 O-GlcNAc
丝氨酸和苏
氨酸衍
生物 8a,b。化合物 4a,b 与三
氯乙酰亚
氨酸 3 的高产 O-糖基化反应,以及 N-乙酰基取代 N-Teoc基团的简易性,促使人们使用 Nα-Fmoc 保护的
丝氨酸和苏
氨酸烯丙基酯(9a、b)和 Pfp 活性酯(12a,b)作为受体,从而非常有效地得到相应的 O-(N,O-乙酰
氨基葡萄糖)
丝氨酸和苏
氨酸衍
生物 11a,b 和 14a,b 活性酯。