Stereoisomers are isomeric molecules that have the same molecular formula and sequence of bonded atoms (constitution), but which differ in the three-dimensional orientations of their atoms in space. Also, they have same physical and chemical properties making regular HPLC stationary phase ( C8, C18, Silica etc) unable to distinguish between them (hence can't separate). You need a column which can form di-stereoisomers (which has different physical and chemical properties) with the compounds of interest. So far there are no such columns (chiral) available in lower partical size (sub 2miron) to make these kinds of separations faster. If you want, you can use the same HPLC Chiral columns on UPLC and develop the separations.
I hope this helps!
an alternative to a chiral column could also be to use a chiral derivatization agent, forming diastereomers which then can be separated on a C18 column. An article with some agents is
H. Brueckner, C. Keller-Hoehl, Chromatographia 40 (1990) 621
I used the FDVA (5-fluoro-2,4-dinitro-valine-amide) for the derivatization and separation of Hydroxyproline-Isomers (3/4-Hyp, cis/trans Hyp, L and D). I have not tested such a separation on UPLC so far, but I cannot imagine why it should not work.