the solution was stirred at room temperature monitoring the reaction by 1 h nmr indicated that the reaction was completed after four hours the reaction mixture was concentrated under reduced pressure at 35 u00b0 c to 1 4 of its original volume and diluted with acetone 100 ml to give an oily product the latter was isolated by decantation and triturated with acetone to afford a solid product 7 75 g which was isolated by filtration and dried under high vacuum nmr data indicated that the product which was identified by the acronym 34 c4s 4k tpa 34 existed as hydrated aldehyde form g synthesis of the aldehyde reagent c4s 4k aba chondroitin 4 sulfate 22 2 g 5 55 mmol and 4 aminobutyraldehyde diethoxyacetal 7 6 g 47 0 mmol were combined in 120 ml of water the ph was adjusted to 8 35 with 1 00 n hcl ethanol 60 ml was added followed by borane pyridine complex 5 7 ml the solution was heated at 40 u00b0 c for six days the solution was cooled and the ph was adjusted to 10 00 with 5 00 n naoh to the stirred solution was added 1 l of ethanol the mixture was stirred for two hours and the precipitate was collected by filtration the solid was washed with ethanol 75 ml followed by ethyl ether 75 ml the solid was dried under vacuum to give 21 5 g of product which was identified by the acronym 34 c4s 4k abda 34 the product was negative to 2 3 5 triphenyltetrazolium chloride indicating that.