1254
COMNCNICATIONS 'ro THE EDITOR
\-u1 X"
(j.0; N , 7.3; A$:;v Hicl 265, 350 nip, log 4.34, small gratings. Averages of components split by ~ - Rr 0.02), 9-amino-6-demethyl-6- crystal effects are given when only data on solids 4.21, [ a . 1 2 5 191", .5- are available. The results are Co(CO)d-: 18S6deoxytetracycline (XII, found for C21H23N30i.1 H20: C, 54.8; H , 5.8; N, 8.9; "A,: HC' 265, (vs), 555(s), 530(w); Fe(C0)4-: 1786(vs), G46(s), 350 nip, log E 4.33, 4.25, [aIz5D -212',& 0.01"),and 55R(m); HFe(C0)4-: 2015 (w), 1937(sh), 18979 - amino - G - deoxytetracycline ( X I I I , found for (vs), 693(m), 618(s), 594(m), 540(w), 513(?); CzzHzsN30i.C4H90H.2H2S04: C, 43.7; H, 5.4; hIn(C0)5-: 1898(vs), 1863(vs) 6S3(s), 659(s), N, 6.2; A ~ ~ ~ v H265, c ' 350 mp,log ~4.26,4.17,[cY]'~D 564(w), 51 1(m), 467(m) The two stronger - 211°, lif0.02). bands of Co(C0)4- previously were reported by Bromination and nitration of 9-amino-6-deoxy- Friedel, et d . , I while those for Fe(C0)4" and HFetetracycline under the previously described condi- (CO)4- correspond, with several exceptions, to tions yielded 9-amino-7-bromo-6-deoxytetracyclineRainan lines recently found by Stammreich and (XIV, found for C22H24N307Br"20.2H2S04 : C, co-workers. 36.0; H , 4.5; N , 10.9;: : :A H C 1 265, 345 mN, The C-0 stretching frequencies in isoelectronic, log E 4.31, 4.07, [a]"D - 153",& 0.44) and %amino- isosteric series have significance in relation t o a 7-nitro-6-deoxytetracycline (XV, found for Cz:- simplified molecular orbital model of the bonding.a H24hr409.2H2S04: C, 38.8; H, 4.7; K,8.0;";:A: I' Following the lead of Edgell and Gallup,4the "lone261, 348 mp, log e 4.32, 414, [ a I z 5 -300", ~ At pair" uco, the TCO and the T*CO orbitals of carbon 0.48), respectively. The position of the bromo monoxide and the 3d, 4s, and 4p orbitals of the and nitro groups in the aromatic ring was proved metal are considered as starting orbitals. Conby the use of tritium labeled starting material. sider the case of the hf(CO)4 species. Using syrnThe relative in vitro antibacterial activities of metry and rough energy arguments, the lower the conipounds described in this paper are presented energy or "B orbitals" of the molecular species in Table I. consist of nine bonding orbitals plus three, nonTABLE I bonding, TCO orbitals. The five remaining ocI n V i h ASTIBACTERIAL ~ A ! i IS ~yo COMPARED ~ ~ ~ TO ~7- ~cupied ~ or "A orbitals" may be thought of as closCHLOROTETRACTCLISE~ ing an electron shell. When the relative energics of the T*CO orbitals are so high that they make no 6-Deoxytctracycline (I) 18 contribution to the A subshell orbitals, the latter 6-Dernethyl-6-deoxytetracycline (11) 40 will be antibonding between the metal and the CO 7-Brorno-6-detnetliyl-6-de~xytetrac~~line (111) GO groups. But with energy decrease, the addition i-Iodo-6-deniethyl-6-deoxytetracycline (11') 30 of T*COcharacter to the A orbitals may be ex7-Bromo-6-deoxytetracycline (1;) 30 pected to result in energy stabilization of this ~ - I o d o - 6 - d e o x ~ ~ t e t r a c ~ (cV l iIn)e 11 subshell, a reduction in metal-CO antibonding ~-Sitro-G-dc~~ietliyl-B-deor;ptftrac~cline (VII) 160 character, and the appearance of C-0 antibondiq 9-~-itro-B-demetli~l-B-deox)-tetracycline (1'111) 3 character. Thus, the .rr*co Character of the -4. ;-Nitro-R-deox)tetrac).cline (IS) Gn* orbitals is an important factor in the bonding dcY-Kitro-6-deox)-tetracycline ( X )
