2,5-Diazabicyclo[2.2.2]octane-3,6-dione-1,4-dicarboxylic acids: synthesis, resolution, absolute configuration and crystal structures of the racemic and (–)-enantiomeric forms

Chirality-directed co-crystallization of different configurationally opposite dialkyl 2,5-diazabicyclo[2.2.2]octane-3,6-dione-1,4-dicarboxylates

“…The absolute configuration of the diesters follows from the fact that the consecutive transesterification (+)-1 ® (+)-2 ® (+)-3 gives (1S,4S)-(+)-3, the configuration of which was found by chemical correlation. 4 Moreover, the opposite configuration of diesters (-)-1 and (+)-2 (Figure 1) follows from the results of X-ray diffraction analysis of [CD(-)230]-4. The absolute configurations of (1S,4S)-(+)-and (1R,4R)-(-)-1 were independently supported by the CD data.…”

“…Note that the formation of columns was not observed in (±)-A. 2 In the case of (-)-1 and (-)-B, 4 the C-H•••O contacts 13 between hydrogen atoms of the C(7)-C(8) bridge and oxygen atoms of the lactam groups, which are typical of the majority of the bislactams examined [4, (±)-A and (-)-A, 2 (±)-1 3 and (±)-B 4 ], are absent.…”

“…In racemic bislactams of the C 2 symmetry, the chirality-directed stereospecific self-assembling of molecules in the crystal by H-bonding into infinite linear zigzag tapes for A, 1,2 (±)-1, 3 diagonal zigzags for C, 4 D 5 and double zigzags (helices) for B 4 with the formation of centrosymmetric crystals was observed.…”

“…ref. 4). The absolute configuration of the diesters follows from the fact that the consecutive transesterification (+)-1 ® (+)-2 ® (+)-3 gives (1S,4S)-(+)-3, the configuration of which was found by chemical correlation.…”

“…Like the case of (-)-A, 2 expected cyclohexamerization 2 does not occur in the crystal structure of (-)-1, although similar H-bonded aggregation of molecules was observed previously (trimerization in solution 10 and hexamerization in crystals of trimesic acid, isophthalic acid derivatives 11 and tetralactams, which form molecular tectones 12 ). Similarly to (-)-B and (±)-B, 4 molecules in a crystal of (-)-1 are joined by H-bonds with the participation of CONH and CO 2 groups into helical suprastructures which can be considered as infinite double zigzag tapes (Figure 2). In this case, the molecules are packed in infinite columns as well as in crystals of 4, (-)-A 2 and (±)-1 3 with similar values of the parameter d 1 = 5.534 Å (cf.…”