Synthesis of an octasubstituted galactose zinc(II) phthalocyanine

4,5-Bis(1,2:3,4-di-O-isopropylidene-α-d-galactopyranos-6-yl)phthalonitrile (3) was prepared by S_NAr reaction of diacetone galactose 1 and 4,5-difluorophthalonitrile (2) in 96% yield. Cyclotetramerization of 3 was achieved via its isoindoline derivative 4, affording the peripherally octasubstituted galactose zinc(II) phthalocyanine 5 in 29% yield. Deprotection of 5 gave the highly water soluble octasubstituted galactose zinc(II) phthalocyanine 6 in 81% yield which will be applied as a photosensitizer in photodynamic therapy.