Cyclohexane twist boat

Identify the lowest-energy conformer from among those provided cyclopropane, planar and puckered cyclobutane, planar and puckered cyclopentane and chair, half-chair, boat and twist-boat cyclohexane. (If... 

Guella G, Chiasera G, Pietra F (1992) Conformational Studies of Marine Polyhalogenated a-Chamigrenes Using Temperature-Dependent NMR Spectra. Inverted Chair and Twist-Boat Cyclohexane Moieties in the Presence of an Axial Halogen Atom at C(8). Helv Chim Acta 75 2026... 

According to the foregoing analysis, conformers such as gauche- and anri-butane or chair and twist-boat cyclohexane would be considered to be diastereomers of each other. However, under most conditions these conformers interconvert so rapidly that butane and cyclohexane are considered to be single species and not mixtures of stereoisomers. When we have to write chemistry books for people living on the outer planets of the solar system, we might have to modify these concepts. 

Twistane (134), first synthesized in racemic form by Whitlock (133) as early as 1962, is composed of four twist-boat cyclohexane moieties with the same chirality, corresponding to a symmetry number of 4, which is inherent in its D2 symmetry. Our group (134) synthesized this interesting compound in an optically active modification. We started from (-)-bicyclo[2.2.2]octanecarbox-ylic acid 146 (Figure 18), which was converted to (+)-twistane (134) via the ketone 147, but our application of Djerassi-Klyne s empirical rule (135) to this intermediate ketone 147 led us to an erroneous conclusion as to abolute configuration. 

Twistanone (147) was found peculiar in its outstanding inertness toward these microbial reductions, and this reluctance was also found in D2(j bisnor-adamantanone (163), though to a lesser extent. This has been attributed to the presence of the protruding methylene group opposite the carbonyl function across the twist-boat cyclohexane ring. 

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