A13C‐NMR study of squalene. Part II. Functionalized squalene‐like compounds

Abstract 13C‐NMR chemical shifts of substituted squalenes and model compounds with a heteroatom in δ‐position to a double bond show that a steric interaction exists between the hetero‐atom and the double bond. This points to the presence of “precoiled” conformations in the hetero‐substituted squalenes and also in squalene itself. The nature of the interaction remains veiled, but it appears to be a general feature as is shown in a series of 2‐ and 3‐substituted thiophenes with a double bond in the side chain.