1-deoxy-D-xylulose 5-phosphate is converted to 2-C-methyl-D-erythritol 4-phosphate in the presence of NADPH. It is involved in the synthesis of isopentenyl diphosphate (IPP), a basic building block in isoprenoid, thiamin, and pyridoxal biosynthesis. [Biosynthesis of cofactors, prosthetic groups, and carriers, Other]