Z′ = 2 crystallization of the three isomeric piridinoylhydrazone derivatives of isosteviol

Abstract

Inclusion of an “extra” molecule in a unit cell as a “cost” of transferring a robust mirror-symmetrical H-bonding motif from a racemic environment into a homochiral one was presented.

Diterpenoids of terrestrial origin

“…127 The ease of isolation of isosteviol by treatment of the crude extracts of S. rebaudiana with acid has led to a number of studies of its chemistry including the formation of glucuronic acid conjugates, 128 macrocyclic and polyethylene glycol esters, 129,130 triazole conjugates, 131 urea 132 and isoniazid derivatives. 133 A number of new tetracyclic diterpenoids have been isolated including 14b-hydroxy-3-oxo-ent-kaur-16-ene from Croton kongensis (Euphorbiaceae), 134 1a,3a,7b,18-tetrahydroxy-ent-kaur-16-ene (sideripullol A) from Sideritis pullulans, (Lamiaceae), 135 3-keto-6b,19-dihydroxy-ent-kaur-16-ene from a Saudi Arabian propolis, 136 7a,15b-dihydroxy-ent-kaur-16-ene from Hyalis argentea (Asteraceae) 137 and a glycoside related to atractyligenin from Vigna angularis (Leguminosae). 138 A further group of diterpenoid glycosides related to cafestol have been obtained 139 from coffee beans.…”

Structural aspects of partial solid solution formation: two crystalline modifications of a chiral derivative of 1,5-dihydro-2H-pyrrol-2-one under consideration

“…Although the number of symmetry-independent molecules does not relate to the enthalpy or entropy of a solid phase directly, in all probability, Z′ > 1 provides more flexibility to accommodate the packing, which could contribute to or contradict the best crystal formative motif. 23,[28][29][30] Moreover, the presence of a second and more "extra" symmetrically independent molecule in crystals is often accompanied by the pseudosymmetry phenomenon, 31 which we exemplified earlier in glycerol derivatives 20,21 and a pair of mucochloric acid polymorphs.…”