In this paper, I discuss a new construction in Brazilian Portuguese, whereby the negative marker não ‘not’, which is syncretic with other types of negation in the language, appears in the slot [Aux_V] in periphrases, a position that is not common in other Romance languages. Among its properties, this type of negation must receive intonational stress, that is, it is a focus element and, as such, it conveys a specific meaning. A comparison with other types of low negation in the same position in Italian, Catalan and French shows that the new negator in Brazilian Portuguese is not the same as the ones that may occur in those languages. Observing this negation marker in relation to low adverbs and to the lexical verb in progressive and perfective periphrases in Brazilian Portuguese, I propose a syntactic position based on the nanosyntax approach, which can explain its focus nature and semantic/pragmatic properties.