AbstractA relatively simple route to 2‐substituted adamantane derivatives labelled with14C at the 2‐position in the adamantane skeleton was developed. The approach used (Figure I) involved ring expansion of adamantanone by labelled diazomethane, conversion of the resulting 4‐homoadamantanone (II) to diazoketone IV, followed by photolytic Wolff ring contraction to 2‐adamantanecarboxylic acid‐2‐14C (VI). Reduction of the carboxylic acid by conventional procedures gave 2‐methyladamanta