| Summary: | Understanding the host–guest chemistry of α-/β-/γ- cyclodextrins (CDs) and a wide range of organic species are fundamentally attractive, and are finding broad contemporary applications toward developing efficient drug delivery systems. With the widely used β-CD as the host, we herein demonstrate that its inclusion behaviors toward an array of six simple and bio-conjugatable adamantane derivatives, namely, 1-adamantanol (adm-1-OH), 2-adamantanol (adm-2-OH), adamantan-1-amine (adm-1-NH<sub>2</sub>), 1-adamantanecarboxylic acid (adm-1-COOH), 1,3-adamantanedicarboxylic acid (adm-1,3-diCOOH), and 2-[3-(carboxymethyl)-1-adamantyl]acetic acid (adm-1,3-diCH<sub>2</sub>COOH), offer inclusion adducts with diverse adamantane-to-CD ratios and spatial guest locations. In all six cases, β-CD crystallizes as a pair supported by face-to-face hydrogen bonding between hydroxyl groups on C2 and C3 and their adjacent equivalents, giving rise to a truncated-cone-shaped cavity to accommodate one, two, or three adamantane derivatives. These inclusion complexes can be terminated as (adm-1-OH)<sub>2</sub>⊂CD<sub>2</sub> (<b>1</b>, 2:2), (adm-2-OH)<sub>3</sub>⊂CD<sub>2</sub> (<b>2</b>, 3:2), (adm-1-NH<sub>2</sub>)<sub>3</sub>⊂CD<sub>2</sub> (<b>3</b>, 3:2), (adm-1-COOH)<sub>2</sub>⊂CD<sub>2</sub> (<b>4</b>, 2:2), (adm-1,3-diCOOH)⊂CD<sub>2</sub> (<b>5</b>, 1:2), and (adm-1,3-diCH<sub>2</sub>COOH)⊂CD<sub>2</sub> (<b>6</b>, 1:2). This work may shed light on the design of nanomedicine with hierarchical structures, mediated by delicate cyclodextrin-based hosts and adamantane-appended drugs as the guests.
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