Twist-Brendanes

Eaton and Leipzig chose to resolve racemic trishomocubanone by reaction with /-ephedrine and separation of the diastereomers by fractional crystallization. Subsequent acid hydrolysis delivered the enantiomeric ketones Successive removal of a diagonal CHj bridge from —)-451 furnishes (—)-ditwist-brendane (Cj symmetry) 454) and (—)-twist-brendane C symmetry) 455). Also,... 

The rearrangements of cage-like structures have been discussed in some detail in refs. 11 and 12, and can be divided into three main classes (i) homocubane to cubane (ii) adamantane to noradamantane and (iii) homoadamantane to twist-brendane and these are depicted (together with strain energy estimations from ref. 79) in Scheme 39. It can be seen that in each case rearrangement provides a system with... 

The optical rotation values [o ]d 3b, 44, 45, 47-49) significantly decrease in the series twistane (s3), twistbrendane 44 and brexane 45. This can be interpreted in terms of helicity as follows Whereas the twistane molecule 3 contains five 6-membered rings in the twist conformation of equal helicity, in the case of brendane 44 there are only three 6-membered and two less twisted 5-membered rings brexane 45 only contains two 6-membered and three 5-membered rings. 

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