Tetramethylsuccinic anhydride can be used to protect the exocyclic amine of 6-aminopurine derivatives by forming the corresponding tetramethysuccinimide. X-ray crystallography confirms that the imide carbonyl and the methyl groups are positioned to sterically block the N7 nitrogen so that glycosylations occur with very high regiochemical control at N9. This approach is particularly effective for 3-substituted purines where the substituent tends to block access to N9 and inhibit glycosylation at that site.

中文翻译：

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四甲基琥珀酰亚胺作为嘌呤糖基化中的指导/保护基团

四甲基琥珀酸酐可通过形成相应的四甲基琥珀酰亚胺来保护6-氨基嘌呤衍生物的环外胺。X射线晶体学证实，酰亚胺羰基和甲基被定位成在空间上阻断N 7氮，使得糖基化在非常高的区域化学控制下在N 9处发生。该方法对于3-取代的嘌呤特别有效，在3-取代的嘌呤中，取代基往往会阻止其接近N9并抑制该位点的糖基化。