Synthesis of novel derivatives of closo‐dodecaborate anion with azido group at the terminal position of the spacer

Abstract

Two novel azido-derivatives of closo-dodecaborate anion with hydrophobic and hydrophilic spacers were prepared by reaction of tetrabutylammonium azide with cyclic oxonium derivatives of the closo-dodecaborate anion. The compounds prepared can be regarded as precursors of derivatives of closo-dodecaborate anion with amino group at the terminal position of a spacer or as building blocks for 'click chemistry', which are useful for preparation of various conjugates with targeting molecules. A concentration dependence of the 11 B NMR spectra of functionalized derivatives of closododecaborate anion was discovered, which is of great importance for analytical purposes.

Practical synthesis of 1,4-dioxane derivative of the closo-dodecaborate anion and its ring opening with acetylenic alkoxides

“…Recently, we reported the 1,4-dioxane ring opening in [B 12 H 11 O(CH 2 CH 2 ) 2 O] À by treatment with various nucleophiles, including azide [14], phenolate [30], and diethylmalonate [31] anions and amines [32]. Similar approach was used here for synthesis of closo-dodecaborate-based acetylenes.…”

“…For this reason, alkyne and azide derivatives of the closo-dodecaborate anion would be potentially useful for direct conjugation to carrier molecules using ''click chemistry" approach. Recently we reported synthesis of azide derivatives of the closo-dodecaborate anion [14] and their conjugation with various acetylenes [15] including acetylene-containing sugars [16]. In this contribution we describe practical synthesis of the 1,4-dioxane derivative of closo-dodecaborate anion, its ring opening with acetylenic alkoxides as well as cycloaddition of the formed acetylene derivative to aromatic azide.…”

Development of Albumin‐closo‐Dodecaborate Conjugates as Boron Carriers for Neutron‐Capture Therapy by Ru(bpy)3‐Photocatalyzed Modification of Tyrosine

“…The formation of dioxane complex 3 by B-H functionalization of closododecaborate followed by nucleophilic ring opening was performed according to the method reported by Bregadze et al [28] N-Hydroxysuccinimidyl ester conjugated TRT 7 was obtained by condensation of the carboxylic acid and N-hydroxysuccinimide resulting from ligation of glutaric anhydride (6) and N,N-dimethylphenylenediamine (5). Amide linker type TRT-DB 1 was synthesized by nucleophilic substitution of amine 4 and 7 in the presence of N,N-diisopropylethylamine (DIPEA) in 84 % yield.…”

“…All chemicals and purified proteins for biological experiments were obtained from commercial sources and were used without further purification. [26] Dioxane-linked closo-dodecaborate 3 was synthesized according to the method reported by Bregadze et al [28] To a solution of 3 (1.22 g, 2.58 mmol) in CH 2 Cl 2 (20 mL) was added tetrabutylammonium azide (1.47 g, 5.17 mmol). The mixture was stirred at room temperature for 24 h and was then concentrated under reduced pressure.…”

“Chemical Ligation”: A Versatile Method for Nucleoside Modification with Boron Clusters

“…Considering utilization of the azide and alkynoxy nucleophiles for oxonium ring-opening, an additional known example is cleavage of the [B 12 H 12 ] 2À tetrahydrofurane adduct. [21][22][23] It may be expected that the greater accessibility to two kinds of metalloborane building blocks bearing either terminal azide groups or terminal triple bonds will further enhance the usability of the "click chemistry" approach in the design of molecular constructions based on various boron clusters. A broad range of applications can be expected in the emerging field of the bioorganic chemistry of boron compounds as pharmacophors.…”