The title β-d-ManNAcA-donor, the α-bromide of methyl 2-benzoyloxyimino-2-deoxy-d-arabino-hexopyranuronate 9, has been prepared from d-glucuronolactone in an overall yield of 21% for the seven steps required, all intermediates being securable in crystalline form. Key compounds were the 2-acetoxy-d-glucuronal ester 6 and its hydroxylaminolysis product, the 1,5-anhydro-d-fructuronate oxime 7, the latter elaborating 9 on O-benzoylation (→8) and photobromination. —The utility of 9 as a suitable β-d-ManNAcA donor rests on two ensuing reactions: first, Koenigs-Knorr type glycosidations, with N-blocked 2-aminoethanols as spacer substrates, or with the 6-OH of an otherwise protected glucoside (16), produce β-selectivities of 20 : 1 or better, and second, the oxime reduction of the β-glycosides, thus obtained, proceeds in an essentially stereospecific manner to yield, upon N-acetylation, the 2-acetamido-2-deoxy-β-d-mannosiduronates. —The methodology elaborated was used to prepare some novel artificial glycolipids, e.g. the (myristoylamino)ethyl 6-O-(2-acetamido-2-deoxy-β-d-mannopyranosyluronic acid)-α-d-glucopyranoside (25) and its (stearoylamino)ethyl analog (26), that are being evaluated as recognition markers for liposomes.
标题为β-d-ManNAcA供体的化合物,甲基2-苯甲氧基
亚胺-2-脱氧-d-
阿拉伯六糖糖醛酸α-
溴化物9,已从d-
葡萄糖醛内酯合成,七个步骤的总体产率为21%,所有中间体均能以晶体形式获得。关键化合物是2-乙酰氧基-d-
葡萄糖醛酯6及其
羟胺水解产物
1,5-脱水-d-果糖醛酸
肟7,后者通过O-苯甲酰化(→8)和光
溴化进一步合成9。——作为合适的β-d-ManNAcA供体,9的利用基于两个后续反应:首先,以N封闭的2-
氨基
乙醇作为间隔底物,或以其他保护的糖苷的6-羟基(16)进行Koenigs-Knorr型糖苷化反应,产生β选择性达到20:1或更高;其次,通过对获得的β-糖苷进行
肟还原,基本上以立体专一性的方式进行,经过N-乙酰化后,得到2-乙酰
氨基-2-脱氧-β-d-
甘露糖醛酸酯。——所开发的方法用于制备一些新型人工
糖脂,例如(肉豆蔻酰
氨基)乙基6-O-(2-乙酰
氨基-2-脱氧-β-d-
甘露糖吡喃糖醛酸)-α-d-
葡萄糖吡喃糖苷(25)及其(硬脂酰
氨基)乙基类似物(26),这些化合物正被评估作为脂质体的识别标记。