On molecular structure of l-nitroarginine

We have found a new form of l-nitroarginine (β-form), which, unlike the known form (α-form) can be obtained in the form of single crystal. The crystal and molecular structures of β-form of l-nitroarginine have been determined and for the first time since the preparation of l-nitroarginine (1911) it has been shown that nitroarginine has zwitter ionic nitrimine structure O2NNC(NH2)NH(CH2)3CH(NH3+)COO- and not nitramine structure as it was believed up to this date. Vibrational spectra of both forms of l-nitroarginine are reported.