Childhood hypersensitivity pneumonitis probably caused by cat hair

One of the mechanisms for multidrug resistance (MDR) of tumors is an overexpression of the P-glycoprotein (P-gp). The cytostatic agent daunorubicin was labeled with carbon-11 to probe P-gp with PET. An enzymatic route for the conversion of carminomycin to 4-methoxy-11C]daunorubicin (4-methoxy-11C]DNR) was investigated, since attempts failed to prepare daunorubicin chemically using 11C]methyl iodide. In the enzymatic synthesis methylation was accomplished by S-adenosyl-L-methyl-11C]methionine (11C]SAM), which was synthesized from L-methyl-11C]methionine. This methylation is catalyzed by carminomycin-4-O-methyltransferase (CMT). The overall radiochemical yield of 4-methoxy-11C]DNR is 1% (EOB), with a total synthesis time of 75 min. In conclusion, 4-methoxy-11C]DNR can be successfully prepared from carminomycin and 11C]SAM using enzymes.