In our studies of deactivated alkylating agents 2, i.e. agents whose alkylating power has been subdued by rendering the nitrogen atom more eleetropositive, we have prepared some quaternary ammonium mustards I which are active against a number of experimental rodent tumors.The chemical mechanism by which the nitrogen mustards, bis(2-chloroethyl)amines, effect alkylation in vitro is well understood 3 and has led to theories concerning the in vivo action of these agents 4. It is generally accepted that the mechanism involves the formation of the very reactive cyclic ethylenimmonium ion s, which, of course, would be impossible in quaternary ammonium mustards. The compounds prepared in the present study were designed to split under certain conditions in vitro" and possibly in vivo (e.g. attack by a nucleophile such as mereaptide), releasing the active nitrogen mustard moiety according to the following equation.The oxazolinium salt IV is the only example ~ of a quaternary nitrogen mustard found active against Yoshida Sarcoma. The authors postulated that IV is activated in vivo by reduction as in bis(2-chloroethyl)-methylamine oxide. On the other hand, the bioisostere 7 V and compounds of the general structure s VI were found inactive against Yoshida Sarcoma and Ehrlich's ascites carcinoma respectively.Preliminary screening * showed that Ia (x=p-NO2CoH4-) was active against DA x° in the range of 0.08-2.5 mg/kg (T.I. n > 30). It was also active against WA ~3 in the range of 1-4 mg/kg (T.I. 11 > 4), and against WM 1-" in the range of 3.5-24 mg/kg (T.I. n > 7). On the other hand, the unsubstituted compound Ib (X = CeH~) and the orthosubstituted compounds Ic (X = o-NO2CoH4-) and Id (X = o-CH~OOCCsH4-) displayed only moderate activity. Against DA ~°, Ib was active at 20-40 mg/kg (T.I. n ca. 2) and Ic was active at 1.25-2.5 mg/kg (T.I. n _~ 2). Id was active at 10-20 mg/kg (T.I. n ~ 2) in WA x3.These results indicate that the quaternary mustards are active against experimental tumors sensitive to biological alkylating agents. (At the same time, Ib, for instance, was inactive in Dunning Leukemia resistant to cyclophosphamide, an alkylating agent.) The fact that electron-withdrawing substituents that do not provide steric hindrance to nucleophilic attack at the benzylic carbon increase the activity of the quaternary mustards seems to support our proposed activation scheme.In another series of compounds, Ie (X = C2H~OOC-) was found to prolong the survival of mice implanted with LE ~4, T/C 15 172%, at 30-50 mg/kg, and to cure WA ~3 at 10-40 mg/kg (T.I. ~t ~ 4) ; If (X = C,HsOOCCH,NHOC-) was active in DA ~° at 4-64 mg/kg (T.I.11 ~ 16), but inactive in cyclophosphamide-resistant Dunning Leukemia.The quaternary ammonium mustards I were prepared by reaction of an ethereal solution of methyl-bis (2-chloroethyl)amine III with the corresponding bromide II (Y = t3r). The products which crystallized from the reaction mixture gave correct analyses.The ideas and results outlined above, in addition to providing leads for preparing new biolo...
