Synthesis of oligogalacturonates conjugated to BSA

The synthesis of three oligogalacturonates with an aldehyde spacer attached at the reducing end is described. Trigalacturonates a-D-GalpA-(1-4)-a-D-GalpA-(1-4)-a-D-GalpA-(1-O(CH2)7CHO and a-D-GalpA(Me)-(1-4)-a-D-GalpA(Me)-(1-4)-a-D-GalpA(Me)-(1-O(CH2)7CHO as well as hexagalacturonate a-D-GalpA-(1-4)-[a-D-GalpA-(1-4)]4-a-D-GalpA-(1-O(CH2)7CHO are prepared by stepwise coupling of galactose units followed by oxidation of the 6-positions. The a-linkages are formed by employing n-pentenyl galactosides as glycosyl donors and N-iodosuccinimide/triethylsilyl triflate as the promoter. Deprotection furnishes the three target oligogalacturonates, which are subsequently linked to bovine serum albumin by reductive amination. These neoglycoproteins will serve as immunogens for generation of new antibodies that can be used for localization and characterization of pectin in plants.