The Crystal Structures of Some Biologically Interesting Molecules

I. Crystals of 1-methylcytosine hydrochloride, C5H8N30+·Cl-, are monoclinic, space group P21/n, with a = 6.695(3), b = 32.30(2), c = 6.912(2) Å, β = 104.22°. There are eight formula units per cell, and hence two per asymmetric unit. Data were collected on an automated diffractometer; the structural parameters were refined to an R index of 0.055 for 2609 reflections. Standard C> deviations in the bond distances are about 0.004 Å. Bond distances in the two structurally distinct molecules are in statistical agreement. The environments of both molecules are closely parallel; features of the structure include layers of molecules joined by N-H···0 and N-H···Cl- hydrogen bonds, relatively short C-H···0 interactions, and close meshing of methyl groups. II. Crystals of lumiflavin-bisnaphthalene-2,3-diol, C13H12N402,2C10H8O2, are moloclinic, space group P21/c with a = 20.78(2), b = 7.24(1), c = 20.15(2) Å and β = 116.19 ± 0.04° [λ(Cu-Kα) = 1.5418 Å]. There are four complexes in the unit cell. Data were collected at Tulane University on an automatic diffractometer, the structure was solved at Caltech using direct methods, and the parameters returned to Tulane for final refinement. This is the first molecular complex of the physiologically active neutral form of isoalloxazine studied. Each flavin is sandwiched between two napthalene molecules with extensive overlap but a moderately large spacing (3.44 Å). III. Crystals of thiabendazole, C10H7N3S, are orthorhombic, space group Pbca, with a = 17.052(7), b = 10.998(4), and c = 10.030(8) Å. There are eight formula units per cell. Data were collected on an automatic diffractometer; the structural parameters were refined to an R index of 0.066 for 1805 reflections. Standard deviations in bond lengths are about 0,006 Å for bonds involving carbon and nitrogen and about 0.003 Å for bonds involving sulfur. The two ring systems are approximately planar 9 but twisted by 9°55' with respect to each other. The C-C bond connecting·the two ring systems is 1.442 Å. IV and V Crystals of the title compounds were obtained as intermediates in the syntheses of the terpenes alnusenone and shinone. The X-ray crystal structures were used to confirm the similar stereo chemistry of these compounds. The decahydro-ethoxy-methoxy-trimethylpycene (called Patrone 3) crystallizes in space group Pbca with eight molecules per unit cell. The cell dimensions are a = 7,094(2), b = 11.823(1), and c = 54.973 (5).The decahydromethoxy- oxo-trimethvlchrysene (CHRY) crystallizes in space group Pna21 with four molecules in the unit cell. The cell parameters are a = 29.922(4), b = 7.757(1), and c = 7.630(4) Å. Both molecules are rather flat except for the methyl groups. The packing is determined largely by van der Waal interactions. Both molecules exhibited the configuration expected from the syntheses.