Crystal Structures of Dipeptides Derived from the β-Amino Acids (1R,2S)-2-Aminocyclopentanecarboxylic Acid and (1S,2R,3S)-2-Amino-3-methylcyclopentanecarboxylic Acid

Crystals of the dimeric beta-peptides 13 and 20, derived from (1R,2S)-2-aminocyclopentanecarboxylic acid and (1S,2R,3S)-2-amino-3-methylcyclopentanecarboxylic acid, respectively, were synthesised and studied by X-ray diffraction in order to establish their solid state secondary structural characteristics. Compound 13 crystallises in the monoclinic space group P 2 (1) with cell parameters of a = 5.2682(1) , b = 9.1211(2) , c = 22.4467(6) , beta = 91.3855(9)A degrees, V = 1078.29(4) (3) and Z = 2. Compound 20 crystallizes in the orthorhombic space group P 2 (1) 2 (1) 2 (1) with cell parameters of a = 5.0968(1) , b = 11.5546(2) , c = 43.5414(8) , V = 2564.22(8) (3) and Z = 4. In both cases adjacent molecules are linked by a series of N-H center dot center dot center dot O=C hydrogen bonds to form beta-sheet like structures.