Short Synthetic Route to Benzaldehyde‐Functionalized Idose and Talose Derivatives by Acetoxonium Ion Rearrangements

Abstract

Abstract Carbohydrate–carbohydrate interactions (CCI) are mediated by complexation of metal ions. Angyal postulated on the requirements for hydroxy group arrangement in pyranoses to account for metal‐ion complexation. These requirements are particularly well fulfilled in α‐ido‐ and α‐talopyranosides, whose ring hydroxy groups have all axial and axial‐equatorial‐axial configurations, respectively. Surface plasmon resonance (SPR) and gold‐nanoparticle techniques have proved to be powerful tools to investigate CCIs. Benzaldehyde‐functionalized glycans can be used for attachment to both gold nanoparticles and SPR sensor surfaces. Therefore, benzaldehyde‐equipped ido‐ and talopyranosides were synthesized by the almost forgotten Paulsen acetoxonium rearrangement. This approach provides peracetylated idose and talose in only two steps from common glucose and galactose precursors, respectively, in overall yields of up to 41 % and, therefore, avoids long and laborious procedures to obtain these rare carbohydrates. The derivatives are being used in ongoing CCI studies using SPR to test Angyal's postulate about the structural requirements for hydroxy group arrangements.