Selective phenylation of 5-hydroxy-.beta.-carboline derivatives

In a process for the production of a compound of formula I ##STR3## in which R.sup.3 is C.sub.1-6 alkyl,

• R.sup.4 is hydrogen, C.sub.1-4 alkyl or C.sub.1-4 alkoxy-C.sub.1-2 -alkyl and
• R.sup.5 is a phenyl radical optionally substituted 1-2 times,
• said process comprising reacting a compound of formula II ##STR4## in which R.sup.3 and R.sup.4 have the above-named meaning, with a compound of formula III,
• R.sup.5 --F (III)
• in which R.sup.5 is defined as above, in the presence of a base, the improvement wherein water is added during the reaction in an amount sufficient to suppress the formation of undesired byproducts.