Th. Steiner

l‐Histidyl‐l‐alanine Dihydrate

The title dipeptide, C 9 H 14 N 4 O 3 .2H 2 O, crystallizes as a zwitterion. The side chain of the histidine residue is uncharged. The peptide C=O group does not accept any conventional hydrogen bonds, only C-H...O interactions.

1β-Hydroxy-1α-propargyl-2β-methyl-2-(2-ethoxycarbonylvinyl)cycloheptane

In the crystal structure of the title compound [ethyl 2-hydroxy-1-methyl-2-(2-propynyl)cycloheptane-1-prop -2-enoate, C 16 H 24 O 3 ] the hydroxy and the propargyl groups of neighbouring molecules form cooperative finite hydrogen-bonded chains, C≡C-H...O-H...O=C. In the C-H...O interaction, the H...O separation is 2.32 A.

1,3-Bis(2-methylphenyl)-2-(4-morpholino)isothiourea

The title molecule, C19H23N3OS, consists of two aromatic rings and a morpholine ring attached to an isothiourea moiety. The morpholine ring adopts a chair conformation and the sum of the angles around the N atom is 337.5 (2)°. The molecular conformation is stabilized by an intramolecular N—H⋯N hydrogen bond.

17α-Ethynyl-19-nor-3-oxo-4-androsten-17β-yl Acetate (Norethindrone Acetate)

The steroid skeleton of the title compound, C22H2803, is almost identical to the parent molecule norethindrone. The ethynyl residue donates a C=C-H...O=C hydrogen-bond interaction, with an H...O separation of 2.18 A.

L-Histidylglycinium dichloride

In the title compound, C 8 H 14 N 4 O 3 2+ .2Cl - , the dipeptide His-Gly crystallizes as a dication. The positively charged imidazole moiety of the histidine side chain is tightly coordinated by chloride anions and O-atom hydrogen-bond acceptors in an almost planar configuration.

L-histidylglycinium chloride, C8H13N4O3+.Cl-

The title peptide crystallized as a monocation with a protonated histidine side chain. The molecules form dimers connected by a tight system of hydrogen bonds, which includes an unusually short Cα—H⋯O interaction with a C⋯O separation of 3.030 (3) A.

5-Dimethylamino-8-methyl-2-quinolone

The title compound, C12H14N2O, is a new laser dye. The quinolone ring system is essentially planar. The hydrogen-bonding scheme involves N—H⋯O=C and C—H⋯N interactions.

1,2-Diphenyl-3-benzylguanidine Hydrochloride

In the title compound, 3-benzyl-1,2-diphenylguanidinium chloride, C20H20N3+.Cl−, the guanidine moiety is protonated. Steric strain due to the phenyl substituents leads to distortions of the guanidine skeleton. All three guanidinium N—H groups donate hydrogen bonds to symmetry-related chloride ions.

7β-Hydroxy-7α-(3-propargyl)-3-methylspiro[5.5]undec-2-en-1-one

The title compound, C 15 H 20 O 2 , contains two six-membered rings, one of which is in a chair conformation while the other assumes an envelope shape. The molecules form dimers which are connected by C-H...O hydrogen bonds donated by the propargyl residue. The hydrogen-bonding pattern is composed of finite cooperative C≡C-H...O-H...O=C chains.

Glycyl-l-histidinium Chloride Dihydrate: an Unusual Histidine Conformation

The histidine side chain of the title compound, C8H13N4O3+.Cl−.2H2O, is protonated and is incorporated in a tight N—H⋯X and C—H⋯X hydrogen-bonding pattern. The orientation of the imidazole moiety is unusual and associated with a short intramolecular C—H⋯O=C hydrogen bond from HisCδ—H to the peptide C=O. This configuration has not been observed previously with peptides.