N1-benzenesulfonylgramine and N1-benzenesulfonylskatole: novel 5-HT6 receptor ligand templates.

1-Benzenesulfonyl-5-methoxy-N,N-dimethyltryptamine (3; K(i)=2.3 nM) is a 5-HT(6) receptor antagonist; removal of the 5-methoxy group (i.e., 6; K(i)=4.1 nM) has little impact on receptor affinity. In the present study, it is shown that the aminomethyl portion of 6 can be shortened to gramine analogue 10a (K(i)=3.1 nM); a related skatole derivative 11b (K(i)=12 nM) also binds with high affinity indicating that the aminoethyl portion of the tryptamines is not required for binding. Compounds 10a and 11b represent members of novel classes of 5-HT(6) antagonists.