a pyrimidine nucleobase + D-ribose => a pyrimidine ribonucleoside + H2O
a pyrimidine nucleobase + d-ribose => a pyrimidine ribonucleoside + h2o
a pyrimidine nucleobase + D-ribose => a pyrimidine ribonucleoside + H2O
a pyrimidine nucleobase + d-ribose => a pyrimidine ribonucleoside + h2o