Context. The deuterium fractionation, Dfrac, has been proposed as an evolutionary indicator in pre-protostellar and protostellar cores of low-mass star-forming regions. Aims: We investigate Dfrac, with high angular resolution, in the cluster environment surrounding the UC H II region IRAS 20293+3952. Methods: We performed high angular resolution observations with the IRAM Plateau de Bure Interferometer (PdBI) of the ortho-NH2D 111-101 line at 85.926 GHz and compared them with previously reported VLA NH3 data. Results: We detected strong NH2D emission toward the pre-protostellar cores identified in NH3 and dust emission, all located in the vicinity of the UC H II region IRAS 20293+3952. We found high values of Dfrac ? 0.1-0.8 in all the pre-protostellar cores and low values, Dfrac Conclusions: The high values of Dfrac in pre-protostellar cores could be indicative of evolution, although outflow interactions and UV radiation could also play a role. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).
