  We report on the results of an IRAM-30m search for CO emission lines in three
galaxies at intermediate redshifts. The idea was to investigate the molecular
content of galaxies bright in the infrared at z=0.4-1.5, a redshift desert for
molecular line studies, poorly investigated as of yet. We integrated 8-10h per
source and did not succeed in detecting any of the sources. From our upper
limits, we are able to constrain the molecular gas content in these systems to
less than 4 to 8 x 10^9 Mo, assuming a CO-to-H_2 conversion factor (\alpha=0.8
Mo/(K km s^-1 pc^2)). We stress the current difficulty of selecting sources
with a detectable molecular content, a problem that will be faced by the ALMA
First Science projects.
