The optical resolution of bicyclo[2.2.1]hept-5-ene-2-cyanohydrins using brucine – a crystallographic and molecular-mechanics study

Abstract

The structures of the brucine complexes with (+)-.1 ]hept-5-ene-2-carbonitrile ( 1/1 ) and (7) 2,3-dimethoxystrychnidine-2-hydroxy-7-oxabicyclo [2.2.1 ]hept-5-ene-2-carbonitrile (1/1)} have been determined. The primary interaction in the complexes is a hydrogen bond between the OH group of the cyanohydrin and the most basic N atom of brucine. Molecular-mechanics calculations on the 7-oxa derivative indicate that the enantiomeric cyanohydrin will fit into the same cavity in the brucine matrix at the cost of ca 71 kJ mo1-1.

Intermolecular hinge—a new function of the C–H⋯π hydrogen bond

“…The C-H … p hydrogen bonds stabilizing the ribbons are usually shorter than C-H … p hydrogen bonds between the neighbouring ribbons, 3 and the latter can be replaced more easily by other interactions with brucine or guest moieties. 3,[9][10][11][12][13][14][15][16][17][18][19] CCDC reference number 632635. For crystallographic data in CIF or other electronic format see DOI: 10.1039/b700211d…”

Guest-Induced Supramolecular Isomerism and Chirality of Brucine Inclusion Crystals with Aliphatic Alcohols: A Hierarchical Interpretation

“…5). 34 Actually, the same molecular conformation has been observed in all known crystals of brucine, 30 brucine solvates, 30,31,34 brucine complexes, 32,33,[35][36][37] and brucinium salts. [19][20][21][22][23][24][25][26][27][28][29][38][39][40][41][42][43][44][45] Such a conformer of brucine was observed in all the resultant crystals with aliphatic alcohols with no exception.…”

“…30,31 However, the inclusion crystals with 3,7,8,12,13,14,15,24,29, and 35 have a 32 and pantolactone. 33 All the resultant crystals could be categorized into three structural types of supramolecular isomers composed of common 2 1 helical tape-like assemblies stabilized by weak multiple hydrogen bonds, such as CH/O and CH/ interactions: 29 C10-HÁÁÁO3, C11-HÁÁÁO4 (O3 and O4: methoxy), C23-HÁÁÁO2 (O2: ether), and C20-HÁÁÁ (arene) hydrogen bonds as shown in Fig.…”

“…32 Hydrogen atoms have been omitted for clarity. Carbon, nitrogen, and oxygen atoms are represented by white, gray, and black spheres, respectively.…”

Chiral Discrimination during Crystallization

“…A monolayer structure, similar to that made by 13a•H + molecules as is shown in Figure 4.43, is also formed even when guest chiral compounds are not acids but alcohols 137 and cyanohydrins (Figure 4.45). 138 In the cases of alcohol complexes, the basic nitrogen of 13a, which is not protonated, can make a strong hydrogen bond with the hydroxy hydrogen of the alcohol, playing a highly significant role in the formation of the complex with the guest alcohol.…”