Über Pterinchemie. 73. Mitteilung [1]. Zum Verlauf der katalytischen Reduktion von 7‐Methylpterin

On the Pathway of the Catalytic Reduction of 7‐Methylpterin The catalytic hydrogenation of 7‐methylpterin (VII) in a neutral solution occurs first by the reduction of the 7,8‐double bond (thermodynamically‐controlled reaction) followed by the reduction of the 5,6‐double bond. On the contrary, in an acidic medium like CF 3 COOH, the 5,6‐double bond is reduced first (kinetically‐controlled reaction). The dihydro‐intermediate then undergoes a [1,2]‐H‐rearrangement leading to the formation of the thermodynamically more stable 7‐methyl‐7,8‐dihydropterin (XV) which on further reduction gives 7‐methyl‐5,6,7,8‐tetrahydropterin (VIII). The catalytic reduction of 7‐methyl‐7,8‐dihydropterin (XV) with deuterium gives stereoselectively a sole product with D at C(6) in the equatorial position.