Helical structure of tercyclopropanedimethanol in solution.
Oligocyclopropanes with repetitive stereochemistry occur in two unusual natural products with interesting bioactivity. X-ray crystal structures are available for these compounds but with partially contradicting results. Because the 1H and 13C NMR spectra of oligocyclopropanes are far from trivial to be assigned even at highest magnetic fields, we have prepared a specifically deuterated sample and have applied high field NMR spectroscopy and DFT calculations to determine its conformation. The helix with equal handedness shown in the stereopicture was found for tercyclopropanedimethanol. A dihedral angle of around +40 degrees is the best representation of the experimental data and characterizes, therefore, the dominating helical conformation of tercyclopropanedimethanol with a single repetitive (+)-gauche interunit dihedral angle. This is in full agreement with the crystal structure of the all syn,trans-quinquecyclopropanedimethanol with an R configuration at the termini that also adopted an all (+)-gauche conformation. However, the crystal structure of the title compound and the solution structure are different.
Department of Chemistry, Imperial College, South Kensington, London SW7 2AY, United Kingdom. agmb@ic.ac.uk
Anthony G M
AG
Barrett
Rachel A
RA
James
Gillian E
GE
Morton
Panayiotis A
PA
Procopiou
Christian
C
Boehme
Armin
A
de Meijere
Christian
C
Griesinger
Uwe M
UM
Reinscheid
D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy / Q000379:methods / Q000592:standards; D000432:Methanol / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D011083:Polycyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011407:Propane / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D012015:Reference Standards; D012996:Solutions / Q000737:chemistry; D013237:Stereoisomerism
D011083:Polycyclic Compounds; D012996:Solutions; C516086:tercyclopropanedimethanol; D011407:Propane; D000432:Methanol