The structure of the O-methyl glycoside of the naturally occurring 6-O
-[(R)-1-carboxyethyl]-alpha-D-galactopyranose, C10H18O8, has been dete
rmined. The absolute configuration was considered as R at the 1-carbox
yethyl moiety which had previously been assigned by synthesis. This ab
solute configuration is consistent both with the determined Flack para
meter [0.04(43)] and the previously known configuration of D-galactose
. The conformation of the torsion angle omega, O5-C5-C6-O6, is shown t
o be gauche-trans.