In studies on antitumor antibody-cytotoxic drug conjugates as potential antitumor agents with improved tumor specificity, daunomycin (DM) was first linked to a poly-L-glutamic acid (PLGA) derivative having a single masked thiol group. At the thiol group, DM-linked PLGA was bound to horse anti-rat alpha-fetoprotein (AFP) antibody. The anti-AFP antibody-PLGA-DM conjugate (anti-AFP conjugate, DM/PLGA/Ig molar binding ratio, 7.5/1.2/1.0) retained most of the antigen-binding activity of the parent antibody and was more potent than either unconjugated DM, a conjugate similarity prepared with normal horse immunoglobulin (normal conjugate), or an unconjugated mixture of anti-AFP antibody and DM in an in vitro cytotoxicity assay against the AFP-producing rat ascites hepatoma cell line AH66. Anti-AFP conjugate tended to be less cytotoxic than DM against the AFP-nonproducing rat ascites hepatoma AH272 cells, and in this case there was no difference between the cytotoxicities of anti-AFP conjugate and of normal conjugate.

A series of 6-phenyl-4H-pyrrolo[1,2-a][1,4]benzodiazepines (2) has been prepared with 2-phthalimidomethylfurans (12) and 1-phthalimidoalkane-2,5-diones (15) or 2,5-dimethoxy-2-phthalimidomethyltetrahydrofurans (16) as the key intermediates and subsequently evaluated for CNS activity. The structure-activity data generated indicate that, in general, introduction of the methyl and/or ethyl group(s) in the pyrrole ring and a chlorine atom at the ortho position of the 6-phenyl group increases the activity and that substitution of the above chlorine atom for a fluorine atom decreases the activity. 8-Chloro-6-(2-chlorophenyl)-1,3-dimethyl-4H-pyrrolo[,2-a][1,4]benzodiazepine (2p), the most potent among the compounds synthesized, was equipotent in taming and sedative activities to diazepam. The acute LD50 of 2p in mice was larger than 3000 mg/kg po.

cis-2-Cyclooctene-1,4-dione 1 is prepared starting from 1,3-cyclooctadiene. Photoirradiation of 1 in ether gives a [π2s+2a] dimer, while irradiations in the presence of cyclic dienes give trans- [2+4]cycloadducts. The intermediacy of trans-2-cyclooctene-1,4-dione is suggested.

Recently, there has been considerable interest in the synthesis of cyclooctatrienediones['I and their valence bond isomerslZ1. In the thermolysis of bicyclo[4.2.0]octa-3,7-diene-2,5-dione ( 1 ) which gives tropone, we have suggested the intermediacy of cis,cis,cis-2,5,7-cyclooctatriene-1,4-dione (6) or its cis,cis,trans Quite recently, ChaLoner et a[. have reported the synthesis of the bis(ethyleneketa1) of (6)13]. We here report the synthesis of (6). 131Reduction of (I)[Zb1 with zinc in acetic acid at 90°C gave bicyclo[4.2.0]octa-7-ene-2,5-dione (2) (yield 65 %) whose synthesis by an independent and different method has recently beende~cribed~~l. Flash thermolysis of (2) The conditions for successful bromination were found as a result of the following observation: The 'H-NMR spectrum of (3) in CF3COOH-CF3SO3H (2: 1) exhibits signals at 6=1.50 (dd, J = l l , 9Hz, lH), 4.17 (dd, 11, 9Hz, lH), 5.32 (t, 9Hz, 1 H), 7.5 (m, 3H), and 8.04ppm (dd, 12, 7Hz, 1 H), thus indicating that the species in this solution is 1,6-dihydroxyhomotropylium ion ( 4 ) . Therefore, the appreciable downfield shift of olefin protons of (3) (Japan) [**I To whom all correspondence should be addressed. those in CDCl3 seems to reflect fast equilibrium between (3) and ( 4 ) . Bromonium ions would be expected to react at C-7 of ( 4 ) .Actually, treatment of (3) with NBS in CFKOOH-CH2CIZ(1 : 2)at room temperaturegave the unstable 2-bromo-5,7-cyclooctadiene-l ,4-dione (5). Dehydrobromination of (S), without isolation, with triethylamine afforded, after chromatography on silica-gel (CH,CI,-ethyl acetate, 95 :5), 2,5,7-cyclooctatriene-1,4-dione (6) The 'H-NMR signals of the diene protons of (6) and of (3) are almost the same, thus indicating that contribution of the polar form (6') can be neglected, i.e. (6) is not aromatic.(6) can be hydrogenated with PtO, to 1,4-cyclooctaned i~n e [~* 6J.Compound (6) is stable in aprotic solvents; however, it is unstable in protonic, particularly in acidic, solvents, giving complex mixtures (thin layer chromatography). Dissolution in CF,COOH at room temperature led to complete decomposition of (6).Although the mass spectrum of (6) is very similar to that of ( I ) , thermal decomposition of (6) at 500°C is only slight. This result rules out the intermediacy of (6) in the thermolytic conversion of ( I ) into tropone. The cis,cis,trans-isomer of (6). which, according to Wood~urd-Hqffmann[~~, is expected as the initial product of thermal ring-opening of ( I ) still, however, remains as a possible intermediate. Dilute solutions of the orange-red l-dimethylamino-2,2-bis(9-fluorenylidenemethyl)ethylene ( I )[I1 are slowly decolor-

A series of 5,6,6a,8,9,11a-hexahydroanaphth[1',2':4,5]imidazo[2,q-b]thiazoles (17 and 20) and 5,6,6a,9,10,11a-hexahydronaphth[2',1':4,5]imidazo[2,1-b]thiazoles has been synthesized with cis- and/or trans-1,2-diamino-1,2,3,4-tetrahydronaphthalenes as the key intermediates and subsequently evaluated for immunological activity (effects on antibody formation and delayed-type hypersensitivity reaction). Among the compounds tested trans-5,6,6a,8,9,11a-hexahydronaphth[1',2':4,5]imidazo[2,1-b]thiazole (trans-17a) and (+/-)-5,6,6a beta,8,9,11a alpha-hexahydro-8 beta-hydroxy-9 beta-methyl-8 alpha-phenylnaphth[1',2':4,5]imidazo[2,1-b]thiazole (20a) showed the largest immunological activity in mice with a magnitude comparable to that of levamisole and were found to be considerably less toxic than levamisole in acute toxicological study. The structures of 18a and 20a were determined by X-ray crystallography.