α,α’-Diamino-α,α’-dicarboxyadipic acid tetraester: synthesis, lactamisation and dilactam structure

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

“…(1S,4S)-(+)-1: yield 45%, mp 233-234 °C, the 1 H NMR spectrum (CDCl 3 ) is identical to that described earlier, 3 in the presence of Eu(tfc) 3 the only signal of HN at 6.96 ppm was observed in the spectrum of (+)-1, whereas the signals of HN of enantiomers at 6.94 and 6.97 ppm (∆n = 12 Hz) were observed for (±)-1; [a] D 20 = 38.6° (c 1.9, MeOH); CD spectrum, cell 0.5 mm, ∆e (l max /nm): in H 2 O (c 7.8×10 -3 M): +0.1 (249), -0.7 (237), +6.9 (220), -4. Enantiomeric bislactam diesters 1-3 were prepared according to Scheme 2.…”

“…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.…”

“…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. Table 1).…”

3,7-Diazabicyclo[3.3.0]octane-2,6-diones: synthesis, NMR spectra and structures

“…Bislactams of the 2,5-diazabicyclo[2.2.2]octane-3,6-dione series are capable of self-assembling only into heterochiral H-bonded suprastructures in the form of infinite linear zigzag tapes, which are packed in racemic crystals, [1][2][3] whereas an H-bonded selfassembly of bislactams of the bicyclo [3.3.n]alkane series (n = = 0-3) leads principally either to a heterochiral diagonal zigzag tape or to a homochiral helical structure. 4 The latter occurs in the case of a chiral glycouril such as 2,6-diethyl-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione, which gives conglomerate crystals and readily undergoes spontaneous resolution by crystallisation.…”

Chiral glycouril, 2,6-diethyl-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione: spontaneous resolution, reactivity and absolute configuration

“…Racemic bicyclic bis-lactams (BBL) were observed to selfassemble into the hydrogen bonded heterochiral polymeric linear zig-zag (lz) chains in crystals (Scheme 1), with space groups Pccn (for R = H) 1 and P2 1 /n (for R = CO 2 Et). 2 Therefore, these compounds cannot be spontaneously resolved by crystallisation. It can be assumed that chain termination of hydrogen bonded polymerisation takes place in the case of homochiral selfassembling.…”