While quantum-chemical calculations of vibrational spectra are well established , their applicability for large molecular systems is limited by the required computational effort. This particularly holds for biomolecular systems, as the need to account for solvent effects as well as conformational flexibility and dynamical effects further increases the computational burden. Moreover, for 2D-IR spectroscopy a treatment within the harmonic approximation is not sufficient, as 2D-IR spectra directly probe anharmonicities as well as anharmonic couplings. Even though there has been considerable progress in the development of efficient methods for anharmonic theoretical vibrational spec-3 troscopy , quantum-chemical calculations of biomolecular 2D-IR spectra are only just emerging .