Reexamination of some reactions of 3-(D-galactosylidenehydrazino)-1,2,4-triazino[5,6-b]indole.
Incorrect structures described in the literature for the products of reactions of the title compound 6 were reexamined and corrected. Thus, the product of acetylation of 6 with acetic anhydride in the presence of pyridine was found to be the mono-N-penta-O-acetyl derivative 10 and not the previously described di-N-penta-O-acetyl derivative 7. Assignment of structure 10 was based on 1H NMR data as well as its ability to undergo oxidative cyclization with Br2/AcOH to give 12. The previously assigned structure 7 would be incapable of undergoing such cyclization. The linear structure 12 rather than the angular regioisomer 3c was assigned on the basis of its UV absorption pattern and 1H NMR NOE spectra. Attempted preparation of 7 by increasing the duration of the reaction gave only compound 10. A di-N-acetyl-penta-O-acetyl derivative, however, was obtained with acetyl bromide in the presence of pyridine to which structure 8 rather than structure 7 or 9 was assigned on the basis of 1H NMR NOE studies. Acetylation of the triazolo-triazino-indole 11 gave a product identical to 12; structure 15 previously assigned to this product is, therefore, in error. Finally, the angular annelated structure 3e previously ascribed to the oxidative cyclization product of the 5-methylhydrazone congener of 6 (13) is now rectified to the linear annelated structure 14; the latter was found to be identical to the product obtained by N-methylation of the unequivocally linear 1,2,4-triazolo[4,3-b]1,2,4-triazino[5,6-b]indole 11. Compound 8 was found to exist in the preponderantly populated sickle (bent) conformation 18 in contrast to compounds 10 and 12 which were found to adopt the extended planar zigzag conformations 19 and 20 respectively.
Shaban
M A E
MA
Department of Chemistry, Faculty of Science, Alexandria University, Ibrahimia, Alexandria, Egypt. mae_shaban@hotmail.com
Nasr
A Z
AZ
Morgaan
A E A
AE
D003500:Cyclization; D007202:Indicators and Reagents; D007211:Indoles / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship; D014227:Triazines / Q000737:chemistry*
C480718:3-(D-galactosylidenehydrazino)-1,2,4-triazino(5,6-b)indole; D007202:Indicators and Reagents; D007211:Indoles; D014227:Triazines