for the following products
4-Nitrophenyl 3-O-alpha-D-glucopyranosyl-alpha-D-glucopyranoside | 4-Nitrophenyl 3-O-alpha-D-glucopyranosyl-alpha-D-glucopyranoside | pNP-alpha-Nigeroside and 4-Nitrophenyl 3-O-(alpha-D-glucopyranosyl)-alpha-D-glucopyranoside