A synthetic strategy for novel nonsymmetrical bola amphiphiles based on carbohydrates

A number of novel nonionic bolaform amphiphiles with nonidentical aldityl head groups, 1-(1-deoxy-d-galactitol-1-ylamino)-6-(1-deoxy-d-glucitol-1-ylamino)hexane (4a), 1-(1-deoxy-d-mannitol-1-ylamino)-6-(1-deoxy-d-glucitol-1-ylamino)hexane (4b), and 1-(1-deoxy-d-galactitol-1-ylamino)-6-(1-deoxy-d-mannitol-1-ylamino)hexane (4c) were synthesized by two successive reductive aminations involving 1,6-diaminohexane (1) and the appropriate d-aldohexoses (d-glucose, d-mannose, and d-galactose) using 5% Pd on carbon as the catalyst. Typical reaction conditions were 40 °C, 4 MPa hydrogen and a reaction time of 4.5 h. The compounds were isolated as white solids in yields ranging from 39% to 72%. The intermediate aminoalditols, 1-(1-deoxy-d-glucitol-1-ylamino)-6-aminohexane (3a) and 1-(1-deoxy-d-galactitol-1-ylamino)-6-aminohexane (3b) were obtained as off-white solids in 80–85% yield. The bolaform amphiphiles containing 1-deoxy-d-glucitol head group(s) showed markedly lower melting points than the compounds with the 1-deoxy-d-mannitol and 1-deoxy-d-galactitol head groups, due to the presence of 1,3-syn interactions within the carbohydrate moiety. The novel bolaform compounds are potential starting materials for the synthesis of a broad range of gemini surfactants with nonidentical, carbohydrate-based head groups. A number of novel non-ionic bolaform amphiphiles with non-identical aldityl head-groups e.g. 1-(1-deoxy-d-galactitol-1-ylamino)-6-(1-deoxy-d-glucitol-1-ylamino)hexane (4a), were synthesized by two successive reductive aminations involving 1,6-diaminohexane and the appropriate d-aldohexoses (d-glucose, d-mannose and d-galactose).