Abstract
The unbiased spectral line survey in the 2 mm atmospheric window towards the nucleus of the starburst galaxy NGC 253 is presented. As a result of this frequency scan a number of molecular species, not previously observed in the extragalactic ISM, have been detected. Four out of these detections correspond to sulfur bearing molecules, namely SO2, H2S, H2CS and NS. Altogether with observations of CS, SO and OCS we are able to characterize the sulfur chemistry of this extragalactic source. Observed abundances are compared with selected prototypical Galactic sources. The similarity between the abundance ratios measured in NGC253 and those in the molecular cloud complexes in the Galactic center suggests that large scale low velocity shocks are the main mechanism heating and driving the chemistry in its nucleus.