Andrena wilkella male bees discriminate between enantiomers of cephalic secretion components

Diastereomers of the spiroacetal, 2,8-dimethyl-1,7-dioxa-spiro[5.5]undecane, represent main components of the cephalic secretion from males of the solitary bee, Andrena wilkella. The major compound proved to be of high enantiomeric purity, showing (2S.6R.8S) configuration. Only, the naturally occurring enantiomer attracted patrolling males in the field; its antipode was behaviorally inactive and in a racemic mixture did not inhibit response. The (E,Z) diastereomers were also found to be almost inactive. EAG studies gave the same result as the behavioral tests. The biological function of the spiroacetal is discussed in view of the evolution of the mating behavior in A. wilkella