Synthesis of per-glycosylated beta-cyclodextrins having enhanced lectin binding affinity

A cyclomaltooligosaccharide containing seven alpha-(1-->4)-D-glucopyranosyl units (beta-cyclodextrins) was transformed into heptakis 6-deoxy-6-iodo (1 3) and heptakis 6-amino-6-deoxy (25) derivatives using known procedures. Co mpound 13 was peracetylated and condensed in one pot with the known peracet ylated pseudothiouronium salts of beta-D-glucopyranose (4), B-D-galactopyra nose (5), or beta-D-N-acetylglucopyranosylsamine (6) or with alpha-D-1-deox y-1-thiomannopyranose (8) using cesium carbonate in dimethylformamide, Alte rnatively, peracetylated 4-aminophenyl-alpha-D-mannopyranoside (9) was tran sformed into either extended pseudothiouronium 11 following N-chloroacetyla tion and nucleophilic substitution by thiourea or into 4-isothiocyanatophen yl alpha-D-mannopyranoside 12 using thiophosgene. Each of the four thiolate d sugar derivatives 4-6 or 8 were also coupled to heptakis chloroacetamido beta-CD 26 obtained from heptakis amine 25 after N-chloroacetylation. Furth er incorporation of a hexamethylenediamine spacer arm onto heptakis iodo be ta-CD 13 using thiol derived from mono-Boc derivative 36 and coupling to is othiocyanate 12 after suitable deprotection afforded permannosylated deriva tive 38. Zemplen de-O-acetylation of all beta-CD derivatives provided water -soluble persubstituted compounds containing D-glucopyranosides (18, 30), D -galactopyranosides (19, 31), D-N-acetylglucosaminides (20, 32), and D-mann opyranosides (22, 24, 34, 39), respectively The compounds were then evaluat ed for their relative binding properties toward natural carbohydrate bindin g plant lectins using both microtiter plate competitive inhibition experime nts, double sandwich assays using horseradish peroxidase labeled lectins an d by turbidimetric assays. The plant lectins from Pisum sativum (pea), Arac his hypogea (peanut), Canavalia ensiformis (Concanavalin A), and Triticum v ulgaris (WGA, wheat germ agglutinin) were used for beta-D-glucose, beta-D-g alactose, alpha-D-mannose, and beta-D-N-acetylglucosamine, respectively. Al l persubstituted beta-CDs showed good to excellent inhibitory properties to gether with abilities to cross-link their analogous plant lectins. The capa city of perglycosylated beta-CDs to anchor both microtiter plate-coated lec tins and their corresponding peroxidase-labeled derivatives further confirm ed the usefulness of these multivalent neoglycoconjugates in bioanalytical assays.