1,8-Diazido-3,6-dioxaoctane

In the title mol-ecule, C(16)H(22)S(8)O(2), two S atoms, two O atoms and ten C atoms form a 14-membered ring with a boat conformation. In the crystal, C-H⋯O hydrogen bonds link the mol-ecules into dimers which are further connected into a chain along the a axis by C-H⋯S hydrogen bonds.

3-(Carboxymethyl)-3-azapentanedioic acid (NTA), 3,12-bis(carboxymethyl)-6,9-dioxa-3,12-diazatetradecanedioic acid (EGTA), and 1,4,7,10-tetraazacyclododecane-N,N',N",N'''-tetraacetic acid (DOTA) structures having a 4-nitrophenyl substituent attached via an alkyl spacer to the methylene carbon atom of one carboxymethyl arm of the chelator were obtained by alkylation of 4-nitrophenylalanine with bromoacetic acid (NTA), by reductive alkylation of 1,8-diamino-3,6-dioxaoctane with (4-nitrophenyl)-pyruvic acid followed by alkylation with bromoacetic acid (EGTA), and by alkylation of the trimethyl ester of 1,4,7,10-tetraazacyclododecane-N,N',N"-triacetic acid with the methyl ester of alpha-bromo-4-(4-nitrophenyl)pentanoic acid and subsequent saponification (DOTA). The nitrophenyl-substituted chelators were converted to the corresponding amines by hydrogenation then reacted with thiophosgene to give the protein-reactive aryl isothiocyanate derivatives.

The title 22-crown-6 unit, C(26)H(28)O(6), comprising of three benzo groups and triethyl-ene glycol, was prepared by the reaction of α,α'-dibromo-p-xylene with 1,8-bis-(2-hydroxy-phen-oxy)-3,6-dioxaoctane in the presence of Cs(2)CO(3) with tetra-hydro-furan (THF) and recrystallized from dichloro-methane-hexane (1:20 v/v) at room temperature. In the mol-ecular structure, two O atoms of the central ethyl-ene glycol in the triethyl-ene glycol unit exhibit exo conformations due to intra-molecular C-H⋯O inter-actions. A number of C-H⋯O and C-H⋯π inter-molecular inter-actions contribute to the stabilization of the crystal packing.