Purity >95%. Human embryonic stem cells (hESC), unlike murine ESC, grow in vitro as large flattened two dimensional colonies. Dispersing these colonies, using trypsin to dissociate single hESC, results in massive cell death. Pyrintegrin is a 2,4-disubstituted pyrimidine that, at 2 uM, enhances the survival of hESC more than 30-fold after trypsin-mediated dissociation. It increases integrin-dependent attachment of hESC to extracellular matrices, including Matrigel(tm) and laminin, without significantly impacting cell proliferation. Pyrintegrin increases the binding of the activated Beta1 integrin-specific antibody HUTS-21 and enhances the phosphorylation of multiple growth factor receptors and their downstream kinases, PI3K and MAPK.