Sulfur trioxide-pyridine, selective sulfation with

Sulfur trioxide reactivity can also be moderated through the use of SO adducts. The reactivity of such complexes is inversely proportional to their stabihty, and consequentiy they can be selected for a wide variety of conditions. Whereas moderating SO reactivity by adducting agents is generally beneficial, the agents add cost and may contribute to odor and possible toxicity problems in derived products. CeUulosic material has been sulfated with SO.—trimethyl amine adduct in aqueous media at 0 to 5°C (16). Sulfur trioxide—triethyl phosphate has been used to sulfonate alkenes to the corresponding alkene sulfonate (17). Sulfur trioxide—pyridine adduct sulfates oleyl alcohol with no attack of the double bond (18). 

In the sulfonation of unsaturated alcohols, powerful sulfonating reagents tend to attack the double or triple bond as well as the hydroxyl group consequently, milder reagents are preferred for selective O-sulfation. Studies of the sulfation of oleyl and elaidyl alcohols showed that the purest product (97% purity) was obtained using chlorosulfonic acid-urea, followed by sulfur trioxide-pyridine (96%), sulfamic acid (93%), sulfur trioxide-dioxan (90%) and chlorosulfonic acid-sodium chloride (60%). With sperm oil, the use of chlorosulfonic acid-urea afforded 99% sulfation with 90% retention of the double bond. ... 

Selective -sulfation of CM-chitosan was carried out by the method of Whistler and Kosic [8]. In brief, 7.0 g CM-chitosan (degree of carboxy-methylation, 0.60 degree of deacetyiation, about 70%) was dissolved in water and the sulfating reagent (sulfur trioxide-pyridine, 3 Eqmol/NH2) was added dropwise over 3 h at pH 9-10 (adjusted by 4 M NaOH aqueous solution). The reaction mixture was dialyzed against deionized water to remove impurities and then lyophilized yield, 8.1 g. Only a small amount of the free amino group was observed by the ninhydrin test. The O-sulfations of CM-chitin and -sulfated CM-chitosan were successively followed by the use of the SO -dimethylformamide (DMF) system [9]. The chemical and physicochemical properties of heparinoids are listed in Table 1, together with those of A -sulfated chitosan (S-DAC). 

In pyridine and with a suitably blocked derivative, the same reagent can be used selectively to introduce sulfate acid ester groups thus, 1,2 5,6-di-O-isopropylidene-D-glucose can be sulfated, and, on removal of the cyclic acetal groups, D-glucose 3-sulfate can be obtained as a suitable salt. Sulfur trioxide or chlorosulfonic acid in liquid sulfur dioxide, and sulfur trioxide in halogenated hydrocarbon solvents, pyridine, or iV,A -dimethylforma-mide, can also be employed for sulfation. 

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