LOW-TEMPERATURE SYNTHESIS OF NO-CARRIER-ADDED [C-11] FORMALDEHYDE WITH METAL-HYDRIDES AND PREPARATION OF [1-C-11]1,2,3,4-TETRAHYDRO-BETA-CARBOLINE DERIVATIVES

A comparative study has been performed on the selective reduction of c yclotron-produced [C-11]carbon dioxide to [C-11]formaldehyde with solu tions of various complex metal hydrides at temperatures between -52 an d +25 degrees C. Under optimal reaction conditions, lithium tetrahydri doaluminate gave the highest yield of [C-11]formaldehyde (58%, decay-c orrected), followed by lithium triethylhydridoborate (34%) and sodium tetrahydridoborate (22%). Radiochemically pure [C-11]formaldehyde coul d be obtained with lithium tetrahydridoaluminate and sodium tetrahydri doborate, but not with lithium triethyl hydridoborate. The produced [C -11]formaldehyde was used for the synthesis of [1-C-11]1,2,3,4-tetrahy dro-beta-carboline derivatives by the Pictet-Spengler reaction. (C) 19 98 Elsevier Science Ltd. All rights reserved.