Abstract
The 2‐hydroxy and 2‐hydroxy‐3‐methyl isomers of 5,8‐dimethoxy‐1,2,3,4‐tetrahydro‐1,4‐ethanonapthalene have been characterized by 13C NMR with the aid of lanthanide shift reagents. A definite interaction with a syn oxygen, presumably with the lone electron pairs, and the aromatic carbon 8a has been established. This n‐π γ‐effect is not found with a corresponding methyl group. Examples from the literature also evidence the reality of the γ‐effect, which provides a useful structure assignment tool.

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