2 4 6 triiodobenzylacetate 393 mg 0 50 mmol was dissolved in a mixture of dmso 4 ml and dimethylacetamide 4 ml containing cs 2 co 3 1 80 g 5 52 mmol and 4 bromomethyl 2 2 dimethyl 1 3 dioxolane 1 0 ml the mixture was stirred for 7 days and was then worked up analogous to example 7a purification by preparative hplc gave 115 mg 26 of the pure product 1 h nmr cd 3 od 5 61 5 5 75 m 2h 5 03 5 44 m 2h 3 47 4 55 m 6h 1 98 2 23 m 9h 1 30 1 71 m 12h n n 39 bis acetoxypropionyl n 2 2 dimethyl 1 3 dioxolane 4 yl methyl 3 5 diamino 2 4 6 triiodobenzylacetate 115 mg 0 13 mmol was dissolved in a mixture of methanol 8 ml and water 8 ml and ph was adjusted to 12 with aqueous 1m naoh after 2 5 h ph was adjusted to 1 with 2m aqueous hcl after stirring for 17 h the solution was neutralized with an aqueous nah 2 po 4 buffer and the solvents were removed evaporation purification by preparative hplc gave 65 mg 69 of the pure product 3 5 diamino 2 4 6 triiodobenzylacetate 3 54 g 6 3 mmol and 2 2 dimethyl 1 3 dioxolane 4 carboxylic.