Glycosaminoglycans (GAGs), including heparin (A), are linear oligosaccharides that consist of amino sugars and uronic acids. [1] Many glycosaminoglycans are involved in vital biological functions [2] but still, little is known about the molecular mechanisms responsible for their action. Much progress toward the synthesis of heparin fragments has been reported
[PPh 4 ] Cl ร (300 mg, 0.8 mmol) in water (20 mL) was added to the mother liquor from this crystallization and a white precipitate was formed and collected by filtration, washed with water (2 ร 10 mL), and dried in vacuum at RT to give 277 mg of an anionic mixture. This mixture was separated by multiple preparative TLC on silica gel, using 3 % MeCN/CH 2 Cl 2 as the mobile phase (detection UV 254 nm). The second band, R f 0.5 was collected and washed out with MeCN. Evaporation of the solvent from combined fractions gave pure 4 ร PPh 4 (174 mg, 6 %). White crystals were obtained by diffusion of Et 2 O into a concentrated CH 2 Cl 2 solution of 4 ร PPh 4 . M.p. 350 8C, elemental analysis calcd (%) for C 25 H 27 B 6 P: B 15.33; found B 14.82. 4,5-I 2 -4 ร PPh 4
: A solution of 4 ร PPh 4 (35 mg, 0.083 mmol) in CH 2 Cl 2 (10 mL) was treated with several portions of solid I 2 (total 44 mg, 0.17 mmol) in the presence of NEt 3 (0.5 mL) under stirring at RT for 0.5 h. The mixture was extracted with 5 % aqueous Na 2 S 2 O 3 (20 mL), the CH 2 Cl 2 layer collected and filtered through a short column of silica gel. Evaporation of the filtrate gave pure 4,5-I 2 -4 ร PPh 4 (52 mg, 93 %). White crystals were obtained by diffusion of Et 2 O vapors into a concentrated CH 2 Cl 2 solution of 4,5-I 2 -4 ร PPh 4 . M.p. 210 8C; elemental analysis calcd (%) for C 25 H 27 B 6 PI 2 : B 9.62; found B 9.38.