We report the detection of complex molecules (HCOOCH_3, HCOOH and CH_3CN), signposts of a hot core like region, toward the low mass, Class 0 source NGC1333-IRAS4A. This is the second low mass protostar where such complex molecules have been searched for and reported, the other source being IRAS16293-2422. It is therefore likely that compact (few tens of AUs) regions of dense and warm gas, where the chemistry is dominated by the evaporation of grain mantles, and where complex molecules are found, are common in low mass Class 0 sources.Given that the chemical formation timescale is much shorter than the gas hot core crossing time, it is not clear whether the reported complex molecules are formed on the grain surfaces (first generation molecules) or in the warm gas by reactions involving the evaporated mantle constituents (second generation molecules). We do not find evidence for large differences in the molecular abundances, normalized to the formaldehyde abundance, between the two solar type protostars, suggesting perhaps a common origin.
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