Potential radioprotective agents--VI. Chalcones, benzophenones, acid hydrazides, nitro amines and chloro compounds. Radioprotection of murine intestinal stem cells.

There is an interest and need for new compounds that protect tissues from radiation injury. In cancer therapy, the protection of normal tissue without protecting tumors is one way to increase the therapeutic gain. Thiol compounds are currently in clinical trials, but are limited to some extent by their human toxicities including hypotension, nausea, and emesis. Several new aminochalcones and aminobenzophenones were synthesized and tested for radioprotective activity in mice. All were less active than p-aminobenzophenone itself. Several acid hydrazides were synthesized and tested similarly, but none exhibited significant activity. The high radioprotective activity of 4-nitroaniline was confirmed, but other nitro amines were substantially less active. 4-Chloro-N-methylaniline is as active as 4-chloroaniline, but other chloro aromatics are devoid of significant activity. When compared with the phosphorothioate amyfostine (WR-2721) using the intestinal clonogenic cell survival assay, 1-(p-aminophenyl)-1-propanol (15), p-aminopropiophenone (16), its ethylene ketal (14), and a mixture of the two (17) protected to a great extent, though slightly less than WR-2721. These results suggest that there is direct cellular radioprotection by these non-thiol compounds. The studies further suggest that preclinical toxicity testing of the most protective agents is warranted.

Potential radioprotective agents--IV. Schiff bases.

Twelve Schiff bases were prepared using salicylaldehyde, one with 5-chlorosalicylaldehyde, one with benzaldehyde, and a series of anilines substituted in the m- or p-positions. They were assayed for radioprotective activity in male, Swiss mice irradiated with a nearly lethal dose (950 cGy) of 6 mV photons produced by a linear accelerator, and were compared with the parent amines. Schiff base formation reduced toxicity of the parent amines; its effect on radioprotective activity was erratic, increasing activity in some cases, decreasing activity in others, and having no effect in still others. Radioprotective activity appears to be unrelated to a number of molecular descriptors. The highest radioprotection (100%) was observed for mixtures of p-aminopropiophenone with its Schiff base, or with the Schiff base of 1-(p-aminophenyl)-1-propanol (95%).

Potential radioprotective agents--V. Melatonin analogs. Oral activity of p-aminopropiophenone and its ethylene ketal.

Seven new amides of 5-methoxytryptamine were synthesized and tested for radioprotective activity in mice. One of them, the heptafluorobutyramide 4, is moderately active (57% survivors), the rest demonstrate little or no activity. Of twelve compounds that had been found to exhibit high radioprotective activity by ip injection, only two [p-aminopropiophenone (9) and its ethylene ketal 8] retain that high activity (92-95% survivors) when administered orally. Three are moderately active: p-aminobenzonitrile (10, 55%), 5-methoxytryptamine octanoic amide (11, 50%), and p-aminobenzophenone (12, 48%).

Potential radioprotective agents. 1. Homologs of melatonin.

Homologs of melatonin were prepared by acylation of 5-methoxytryptamine with the appropriate acid chloride or anhydride. The products were administered as solutions or suspensions in soybean oil by ip injection to mice 30 min prior to irradiation with 950 cGy of 6 mV photons. Protection was achieved with all compounds, survival rate being maximal for mice treated with the hexanoic amide 5 and the octanoic amide 6.

Potential radioprotective agents. 2. Substituted anilines.

A series of substituted anilines was examined for radioprotective activity by injecting them ip into mice subjected to a near-lethal dose of 6 mV photons. Electronegative groups such as Br, NO2, CN, and acyl in the meta or para position gave rise to highly active compounds (80-100% protection), while p-amino, methyl, amide, hydroxy, and fluoro groups decrease activity. No general correlations could be developed, however, between biological activity and a wide variety of calculated molecular parameters. The highest activity was found with p-aminobenzophenone (1), p-aminopropiophenone (2), its ethylene ketal (3), 2-amino-5-chloropyridine (35), and 5-amino-2-chloropyridine (36).

Dihydrotestosterone derivatives: relative binding affinity versus affinity purification.

Mono esters of a homologous series of diacids of dihydrotestosterone were synthesized and converted to the corresponding n-butyl amides. The relative binding affinities of these amides to androgen receptor were compared with the degree of purification of rat prostate androgen receptor by affinity columns prepared by linking the steroidal acid to amino Sepharose. There was good correlation between binding of the amide model to androgen receptor and the extent of purification by the affinity resin.

Synthesis and androgen receptor binding of dihydrotestosterone hemisuccinate homologs.

Dihydrotestosterone-succinyl-agarose is the most common form of androgen affinity column. To investigate the effect of variation in the number of methylene groups between the ester and amide functions, a homologous series, varying the number of methylenes between the functional groups, has been synthesized and evaluated. In addition, since structure studies show 17 alpha-methyldihydrotestosterone binds with high affinity, a 17 alpha-carboxymethyl ligand (3) was studied. Relative binding affinities of the dicarboxylates (assayed as the n-butyl amides) range from 0.003 to 0.044 (dihydrotestosterone = 1.00), while there was no detectable binding for 3. Only the suberate binds better than the much-used succinate, and it would be a likely candidate for an affinity ligand.

The anticoagulant effect of hexolame, N-(3-hydroxy-1,3,5(10)-estratrien-17 beta-yl)-6-hydroxyhexylamine, another amino-estrogen with prolonged anticoagulant effect.

The anticoagulant and estrogenic effects of hexolame, N-(3-hydroxy-1,3,5(10)-estratrien-17 beta-yl)-6-hydroxyhexylamine, are described. A single subcutaneous injection of hexolame in adult and infant male mice produced dose-dependent increases in blood clotting time which could be observed even after 2 days. In ovariectomized mice, hexolame produced vaginal cornification (estrogenic response). The data suggested that if used in the treatment of prostatic cancer, hexolame, like prolame, would not induce cardiovascular accidents. It could also be useful in the prevention of thrombosis.

Conjugates of steroids and anti-cancer agents. III. The synthesis of estrynamine and certain derivatives.

Propargyl amine was protected by condensing it with 2,5-hexane-dione to give 2,5-dimethyl-N-(2'-propyn-1'-yl)pyrrole (2). The latter was converted to the corresponding Grignard reagent with ethylmagnesium bromide, and then condensed with estrone tetrahydropyranyl ether to give 17 alpha-[3'-(2'',5''-dimethyl-1''-pyrryl)-1'-propyn-1'-yl)-1,3 ,5( 10)- estratriene-3,17 beta-diol 3-tetrahydropyranyl ether (3), in 85% yield. Acetic acid and methanol cleaved the tetrahydropyranyl ether group, and hydroxylamine and sodium bicarbonate cleaved the pyrrole ring to give 17 alpha-(3'-amino-1'-propyn-1'-yl)-1,3,5(10)-estratriene-3,17 beta-diol (1), estrynamine. Several derivatives and analogs of 1 were also synthesized. Estrynamine binds to estrogen receptor with an RBA of 0.0045 (estradiol = 1.0). Several of the compounds, including estrynamine, are weak estrogens (stimulation of prolactin synthesis).

Synthesis of some analogs of estradiol.

As part of a search for estradiol derivatives designed for conjugation to carboxyl or amine functions of anti-cancer agents or suitable derivatives thereof, estradiol analogs with side chains at the C-16 or -17 position were prepared for biological assay. These analogs include several which have a substituted nitrogenous function at C-17. The avidity of some of these analogs for binding to estrogen receptor was found to be of a low order.

New evaluation of potential methylmercury scavengers.

A biological assay was developed to evaluate rapidly the relative efficacy of marketed and experimental mercurial scavengers. Rat liver mitochondrial protein (1.0 mg) was titrated against methyl-mercuric chloride to the inhibitory level of mitochondrial respiration. Respiration induced by adenosine 5'-diphosphate with succinate (plus rotenone) as the substrate was inhibited consistently by 20.7 +/- 3.9 nmoles of methylmercury/mg of protein. Adenosine 5'-diphosphate-stimulated respiration (State 3) was restored with dimercaprol, penicillamine, and cysteine but not with serine. The antagonists glutathione, 3-mercapto-propionic acid, 2-mercaptoethanol, dithiothreitol, thioglucose, mercaptosuccinic acid, and thiosalicylic acid and mercaptosuccinic acid. Sodium sulfide, thioacetamide, and ethylenediaminetetraacetic acid were completely inactive. Substitution of glutamate (plus malate) for succinate (plus rotenone) as the substrate did not alter the responses significantly. The rat liver mitochondrial assay provides preliminary information about the efficacy and toxicity of water-soluble thiols. Investigations utilizing encapsulated water- and lipid-soluble mercaptans are in progress.

Mercapto steroids in protection against mercury and lead poisoning.

When thiocholesterol is administered as liposomes, it provides significant protection against methylmercuric chloride in mice when given in three intraperitoneal injections, 0.5 hr before and 2 and 8 hr after the methylmercuric chloride. Thiositosterol, 5 alpha-cholestane-2 beta, 3 alpha-dithiol, and 5 beta-cholane-3 beta, 24-dithiol also are active, but 3 alpha-mercapto-5 alpha-pregnan-20-one, 6 beta-mercapto-5 alpha-cholestane-3 beta, 5 alpha-diol, 3 beta-mercapto-5 beta-cholanic acid, and adamantanethiol are ineffective under these conditions. Adamantanethiol is somewhat effective when administered in soybean oil. Cholestanyl amine was treated with acetylthiosuccinic anhydride to give the half amide; cleavage with hydroxylamine liberated the thiol group. This product is active against both methylmercuric chloride and lead nitrate.

Synthesis and evaluation of sulfur-containing steroids against methylmercuric chloride toxicity.

Sulfur-containing steroids, analogs, and derivatives were synthesized for evaluation in mice suffering acute toxicity from methylmercuric chloride. Steroids were administered by intraperitoneal injection, by stomach tube feeding, or by absorption through the tail skin. Thiocholesterol and the thiocholanoic acids were effective if given prior to poisoning. The thiosteroids were significantly more effective than penicillamine or dimercaprol under these conditions.

Total synthesis of 1,11- and 3,11-diazasteroids.

The 2- and 6-methoxy derivatives of 8-aminoquinoline, as well as 5-aminoisoquinoline, condensed with 2-ethoxycarbonylcyclopentanone to give tricyclic intermediates in 86-90% yield. These secosteroids were cyclized in 35-69% yield with polyphosphoric acid to 2-methoxy-1,11-diaza-, 7-methoxy-1,11-diaza-, and 3,11-diaza-1,3,5,7,9,13-gonahexaen-12-ones, respectively. The latter exhibits slight antileukemic activity.

Synthesis of steroidal cyclophosphamides.

The Reformatsky product of estrone methyl ether and ethyl bromo-acetate was transformed by two separate routes to 21-amino-3-methoxy-17alpha-pregna-1,3,5(10)-trien-17beta-ol (9). Cyclization with bis- (2-chloroethyl) phosphoramide dichloride produced the steroidal cyclophosphamide 10. Analogous syntheses transformed androstenolone into steroidal cyclophosphamide 20 and androstenedione into steroidal cyclophosphamide 28.

Total synthesis of diazasteroids (1).

Contrary to previous reports, the condensation product of 8-aminoquinoline (1) and 2-carbethoxycyclopentanone (2) undergoes ring closure with polyphosphoric acid to give the 1, 11-diazasteroid 5. Catalytic hydrogenation reduced the A ring and the double bond to produce 6. 8-Aminotetrahydroquinoline (7) and 3-carbethoxy-2-piperidone condense to a tricyclic intermediate (11), which could not be cyclized to a steroid, however.