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NMR detection of intramolecular OH/OH hydrogen bond networks: an approach using isotopic perturbation and hydrogen bond mediated OH…OH J-coupling

A series of conformationally restricted triol and tetrol systems containing intramolecular hydrogen bond arrays has been prepared and characterized by X-ray crystallography and NMR spectroscopy. NMR isotopic perturbation measurements in DMSO-d 6 and CD 2 Cl 2 reveal that this methodology can be used to detect the spatial proximity of up to four contiguous hydroxyl groups sharing a 1,3-, 1,4-, or 1,5- relationship. Furthermore, hydrogen bond mediated scalar couplings can be used to assign the identity of NMR resonances arising from perturbed OH signals. Our studies suggest that isotope shifts in OH OH networks are additive. An application in the area of natural product structure elucidation is presented.