(E)-4-Hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP or HMB-PP) is an intermediate of the  MEP pathway (non-mevalonate pathway) of isoprenoid biosynthesis.
In the context of isoprenoid biosynthesis, (E)-4-Hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP or HMB-PP) serves as a pivotal intermediate in the MEP pathway, which is one of the primary routes for producing these compounds.