A ladderane is an organic molecule containing two or more fused rings of cyclobutane. The name is a portmanteau because the serial cyclobutane rings look like a ladder and are singly bonded like alkanes. The chemical formula for a ladderane with n rings is C2n+2H2n+6. The geometry of ladderanes is highly strained because ligands to the carbon atoms cannot extend to their ideal angles. However, examples of ladderanes have been found in living organisms. An example ispentacycloanammoxic acid which is composed of 5 fused cyclobutane units. It is found in bacteria performing the anammox process where it forms part of a tight and very dense membrane believed to prevent the organism from losing the intermediate hydrazine which is involved in the production of nitrogen and water from nitrite ions and ammonia.
A simple ladderane, consisting of threefused cyclobutane rings
Back in 2005, Corey and Mascitti prepared the first enantioselective (single mirror image of a compound) synthesis of pentacycloanammoxic acid (JACS 2006, 128,3118-3119). This C20 fatty acid, firstdiscovered in deep-sea bacteria by Dutch researchers in 2002, provides an extremely rigid lipid bilayer to bacterial cell membranes, which biologists believe shields them from their own toxic metabolic byproducts – anammoxic bacteria utilize ammonia for energy, and produce hydrazine (rocket fuel) and hydroxylamine as waste products en route to N2 and H2O.
^ a b Nouri, D H, Tantillo, D J (2006). "They Came from the Deep:Syntheses, Applications, and Biology of Ladderanes". Curr. Org.Chem. 10(16): 2055–2074. doi:10.2174/138527206778742678.^ J. S. Sinninghe Damsté, M. Strous, W. I. C. Rijpstra, E. C.Hopmans, J. A. J. Geenevasen, A. C. T. van Duin, L. A. van Niftrikand M. S. M. Jetten (2002). "Linearly concatenated cyclobutanelipids form a dense bacterial membrane". Nature 419 (6908): 708–712.doi:10.1038/nature01128. PMID 12384695.^ Vincent Mascitti and E. J. Corey (2006). "EnantioselectiveSynthesis of Pentacycloanammoxic Acid". J. Am. Chem.Soc. 128 (10): 3118.doi:10.1021/ja058370g. PMID 16522072.
Linearly concatenated cyclobutane lipids form a dense bacterial membrane Jaap S. Sinninghe Damsté, Marc Strous, W. Irene C. Rijpstra, Ellen C. Hopmans, Jan A. J. Geenevasen, Adri C. T. van Duin, Laura A. van Niftrik and Mike S. M. Jetten Nature 419, 708-712(17 October 2002) doi:10.1038/nature01128
Enantioselective Synthesis of Pentacycloanammoxic Acid Vincent Mascitti and E. J. Corey pp 3118–3119Publication Date (Web): February 16, 2006 (Communication) DOI: 10.1021/ja058370g
"The synthesis of the 3- and 5-ladderanes isa crowning achievement," says chemistryprofessor Bruce M. Foxman of BrandeisUniversity. "The work provides both a newsubclass of solid-state photocycloadditionproducts and an elegant example of howthe careful planning and execution of asolid-state methodology may open thedoor to a simple, high-yield synthesis of anelusive class of molecules."
A solid-state intermolecular synthesis of ladderanes that provides gram amounts of these unusual compounds in quantitative yields has been developed by assistant chemistry professor Leonard R. MacGillivray and graduate students Tomislav Frii and the late Xiuchun Gao of the University of Iowa [Angew. Chem. Int. Ed.,43, 232 (2004)]. Ladderanes feature a series of fused cyclobutane rings that chemists believe could impart unique electronic properties or serve as spacers to separate metals or functional groups for a potential new class of optoelectronic materials. Several groups have made short ladderanes with limited success, building them up from halogenated cyclobutenes, from alkenes and alkynes, or by fusing together polyenes [Angew. Chem. Int. Ed., 42, 2822 (2003)]. One problem, MacGillivray notes, is that in solution the ladder precursors are probably too disorganized to align and react properly.
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