1-METHYLPHENOTHIAZINE AND 1-ETHYLPHENOTHIAZINE 2511 the size of the 1-alkyl substituents and is correlated with the size of the folding angle as in other phenothiazines. All the C-H bond lengths and C-C-H and H-C-H bond angles are within reasonable ranges of magnitudes. The packing of 1-ethylphenothiazine in the crystal is shown in Fig. 3. There are no inter- molecular contacts less than van der Waals distances. This research was supported by grants (N-495 and Y-484) from the Robert A. Welch Foundation, Houston, Texas. The authors wish to thank Dr R. Shiono of the University of Pittsburgh for making the OR TEP plots. References CHU S. S. C. t~. VAN DER HELM, D. (1975). Acta Cryst. B31, 1179-1183. CHU, S. S. C. & VAN DER HELM, D. (1976).Acta Cryst. B32, 1012-1016. CHU, S. S. C., NAPOLEONE, V., TERNAY, A. L. JR & CHANG, S. (1982). Acta Cryt. B38, 2506-2508. CREMER, D. • POPLE, J. A. (1975). J. Am. Chem. Soc. 97, 1354-1358. JOHNSON, C. K. (1965). ORTEP. Report ORNL-3794. Oak Ridge National Laboratory, Tennessee. Acta Cryst. (1982). B38, 2511-2513 M ethyl 4,6-Bis(O-p-ehlorob enzoyl)- 2,3-dideoxy- 3- C-(metho xy e arbonylmethyl)-a-D-r/bo- hexopyranoside BY DAVID L. HUGHES,* RICHARD A. PAUPTIT, EASWARA SUBRAMANIANt AND JAMES TROTTER Department of Chemistry, University of British Columbia, Vancouver, BC, Canada V6 T 1 Y6 (Received 20 November 1981; accepted 7 April 1982) Abstract. Crystals of the title compound, C24H24C1208, Mr = 5i 1.35, are monoclinic, P21, a = 5.752 (3), b = 15.436 (3), c = 13.698 (3) A, fl = 93.74 (3) °, D m = 1.43, D x -- 1.40 Mg m -3, Z = 2. The structure was determined from Cu Ka diffractometer data (with great difficulty), and refined to R = 0.042 for 898 reflexions. The six-membered pyranose ring is in the chair conformation, with the bulkier 4,6-p-chlorobenzoyl substituents equatorial, and the 1-OMe and 3-CH2COEMe groups axial. Bond lengths and angles and intermolecular distances are normal. The ex- tremities of the p-chlorobenzoyl groups exhibit large thermal librations [r.m.s. displacement as large as 0.56 (1) A for one CI]. Introduction. The title compound [(1), R = C1C6H4CO-] is a branched-chain sugar which was of interest because of possible antibiotic properties, and an X-ray crystal analysis was undertaken to verify structural assignments based on NMR data (Rosenthal & Catsoulacos, 1968). The X-ray study was begun in *Present address: Molecular Structures Department, Roth- amsted Experimental Station, Harpenden, Hefts AL5 2JQ, England. t On leave from: Department of Physics, Crystallography and Biophysics, University of Madras, Madras 25, India. 0567-7408/82/092511-03501.00 1967 (by DLH shortly after arrival in Vancouver from Antarctica, after a journey by Land Rover through South America). R O ~ 0 CHzCOzCH B OCH3 3' The unit-cell dimensions were obtained by least- squares refinement based on 28 values for 30 reflexions, and intensities were measured on a Datex automated GE XRD-6 diffractometer with nickel-filtered Cu Ka radiation and a 0--28 scan technique. The scan speed was 1° min -~, with 40 s background measurements before and after the scan. The intensities exhibited a rapid decrease with increasing 8, so that the data set was rather limited. Of 1028 reflexions in the range 0 < 0 _< 45 °, 898 had I/a(I) > 2.0, where tr(I) = S + B + (0.02S) 2, S = scan and B = normalized background count. Crystal dimensions were 0.25 x 0.05 x 0.04 mm, and no absorption corrections were considered necessary (# = 28 cm-~). Early attempts to determine the structure involved Patterson methods and efforts to pack the p-chloro- © 1982 International Union of Crystallography