We will discuss the chemical evolution of the simplest amino acids, glycine in high-mass
stars based on observational results and chemical modeling.


We have conducted survey observations of complex organic molecules, including glycine's
precursors, CH2NH and CH3NH2. As a result, we detected CH2NH towards eight high-mass
star-forming regions. We found that CH2NH rich sources tend to show higher abundances of
other N-bearing species, while the correlation with O bearing species was small. Through
a chemical modeling study under the different physical conditions we found that
different temperature structure may be a key to explain the chemical difference:
observed N-bearing species tend to be easily destroyed on grain surface reactions if the
temperature is low.

Based on this modeling, we developed a chemical modeling towards glycine to reveal its
efficient formation process. Assuming the reactions of suprathermal hydrogen atoms,
which was given extra energy by UV photons, HOCO radicals were efficiently produced from
CO2. As a result, we showed that the reaction of HOCO + CH2NH2 would efficiently form
glycine.

In this talk, I will present these results and its importance in origin of life.