Eudistomin derivatives, novel phosphodiesterase inhibitors: synthesis and relative activity

The preparations of novel phosphodiesterase inhibitors, 8-acetoxy-5-iodo-6-methoxypyrido[3,4-b]indole, 5,7-dibromo-6-hydroxypyrido[3,4-b]indole, 5,7-dichloro-6-hydroxypyrido[3,4-b]-indole and 8-acetoxy-5-bromo-6-methoxypyrido[3,4-b]indole, are described together with concentrations giving 50% inhibition against cyclic AMP phosphodiesterase, i.e. 3 X 10(-6), 3 X 10(-6), 7 X 10(-6) and 1 X 10(-5) M, respectively. The relative potency of these eudistomin derivatives is discussed in terms of the chemical structures compared with those of other inactive eudistomins and derivatives.