  Interstellar amides have attracted significant attentions as they are
potential precursors for a wide variety of organics essential to life. However,
our current understanding of their formation in space is heavily based on
observations in star-forming regions and hence the chemical networks lack the
constraints on their early origin. In this work, unbiased sensitive spectral
surveys with IRAM 30m and Yebes 40m telescopes are used to systematically study
a number of amides towards a quiescent Galactic Centre molecular cloud,
G+0.693-0.027. We report the first detection of acetamide (CH3C(O)NH2) and
trans-N-methylformamide (CH3NHCHO) towards this cloud. In addition, with the
wider frequency coverage of the survey, we revisited the detection of formamide
(NH2CHO) and urea (carbamide; NH2C(O)NH2), which had been reported previously
towards G+0.693-0.027. Our results are compared with those present in the
literature including recent laboratory experiments and chemical models. We find
constant abundance ratios independently of the evolutionary stages, suggesting
that amides related chemistry is triggered in early evolutionary stages of
molecular cloud and remain unaffected by the warm-up phase during the star
formation process. Although a correlation between more complex amides and
NH2CHO have been suggested, alternative formation routes involving other
precursors such as acetaldehyde (CH3CHO), methyl isocyanate (CH3NCO) and
methylamine (CH3NH2) may also contribute to the production of amides.
Observations of amides together with these species towards a larger sample of
sources can help to constrain the amide chemistry in the interstellar medium.
