Bortezomib Impurity (R,S-Isomer),((S)-3-Methyl-1-((R)-3-phenyl-2-(pyrazine-2-carboxamido)propanamido)butyl)boronic acid,"(1S,3R)-Bortezomib is an diastereomer of Bortezomib , the first proteasome inhibitor to be approved by the US FDA for multiple myeloma, a blood cancer. A reversible inhibitor of the 26S proteasome-a barrel-shaped multiprotein particle found in the nucleus",Bortezomib Therapeutic