title: (1R,6R,13R,18R)-(Z,Z)-1,18-Bis[(4R)-2,2-dimethyl-1,3-dioxolan-4-yl]-3,16-dimethyl-ene-8,20-diaza-dispiro-[5.6.5.6]tetra-cosa-7,19-diene.
abstract: The crystal structure of the title compound, C(34)H(54)N(2)O(4), has been solved in order to prove the relative and absolute chirality of the newly-formed stereocentres which were established using an asymmetric Diels-Alder reaction at an earlier stage in the synthesis. This unprecedented stable dialdimine contains a 14-membered ring and was obtained as the minor diastereoisomer in the Diels-Alder reaction. The absolute stereochemistry of the stereocentres of the acetal functionality was known to be R based on the use of a chiral (R)-tris-ubstituted dienophile derived from enanti-opure (S)-glyceraldehyde. The assignment of the configuration in the dienophile and the title di-aldimine differs from (S)-glyceraldehyde due to a change in the priority order of the substituents. The crystal structure establishes the presence of six stereocentres all attributed to be R. The 14-membered ring contains two aldimine bonds [C-N = 1.258 (2) and 1.259 (2) Å]. It adopts a similar conformation to that proposed for trans-trans-cyclo-tetra-deca-1,8-dienes.
authors: Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
authors: Stéphanie M
authors: SM
authors: Guéret
authors: Peter D W
authors: PD
authors: Boyd
authors: Margaret A
authors: MA
authors: Brimble
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