Synthesis of thiourea-tethered C-glycosyl amino acids via isothiocyanate–amine coupling
作者:Reham F. Barghash、Alessandro Massi、Alessandro Dondoni
DOI:10.1039/b908156a
日期:——
A new class of C-glycosyl amino acids displaying a thiourea segment as a linker has been designed and synthesized by addition of peracetylated glycosylmethyl isothiocyanates to an amine-functionalized amino acid (Nα-Fmoc-β-amino-L-alanine). Three pairs of compounds with α- and β-galacto, α- and β-gluco, and α- and β-manno configuration have been prepared with yields ranging between 70 and 75%. The orthogonal set of protective groups (O-acetyl in the carbohydrate moiety and N-Fmoc in the amino acid residue) makes these compounds suitable substrates for the co-translational modification of natural peptides. The couplings of model hydroxy-free and perbenzylated glycosylmethyl isothiocyanates with the above Nα-Fmoc-β-amino-L-alanine and the Nα-Boc-protected analogue have been carried out as well, thus broadening the scope of the coupling reaction. Nevertheless, there are limitations of this isothiocyanateâamine coupling in complex systems, and these are briefly discussed.
通过将乙酰化的糖基甲基异硫氰酸酯添加到胺功能化的氨基酸(Nα-Fmoc-β-氨基-L-丙氨酸)上,设计并合成了一类新的具有硫脲键段的C-糖基氨基酸。制备了三种分别具有α-和β-半乳糖、α-和β-葡萄糖以及α-和β-甘露糖构型的化合物,产率在70%至75%之间。保护基团(糖部分中的O-乙酰基和氨基酸残基中的N-Fmoc)的正交性使得这些化合物适合作为天然肽共翻译修饰的底物。还进行了模型无羟基和苯甲酰化的糖基甲基异硫氰酸酯与上述Nα-Fmoc-β-氨基-L-丙氨酸及其Nα-Boc保护类似物的偶联反应,从而扩大了偶联反应的范围。然而,这种异硫氰酸酯-胺偶联在复杂系统中存在局限性,这些局限性在此简要讨论。