Relative cardiotoxicity and cytotoxicity of anthraquinonyl glucosaminosides.

The cardiotoxicity and cytotoxicity for tumor cells of four new synthetic anthraquinonyl glucosaminosides were compared in vitro. The nonhydroxylated anthraquinone was not cardiotoxic, and its cytotoxic activity was the weakest of the compounds in the series. Increasing the number of hydroxyl groups on the anthraquinone moiety increased the inhibition of growth of L-1210 leukemia cells and pancreatic or colonic adenocarcinomas in a soft agar colony formation assay. However, cardiotoxicity was also increased in proportion to the number of hydroxyl groups present. The adenocarcinomas were slightly more sensitive than the leukemias to the inhibitory action of the dihydroxylated anthraquinonyl glucosaminosides on cell growth.

Synthesis of anthraquinonyl glucosaminosides and studies on the influence of aglycone hydroxyl substitution on superoxide generation, DNA binding, and antimicrobial properties.

A series of anthraquinonyl glucosaminosides (10a-e) were synthesized by Koenigs-Knorr glycosidation of the corresponding aglycones (11a-e) with bromo sugar 12 followed by saponification. These glycosides were intended to serve as models to study the role played by the hydroxyl substituents on the aglycone portion of the antitumor anthracycline antibiotics. Superoxide generation as measured in rat heart sarcosomes was found to increase with the addition of successive hydroxyl groups to the anthraquinone nucleus. The 1,8-dihydroxy pattern was determined to generate significantly less superoxide than the 1,4-dihydroxy pattern. Hydroxyl substitution was also observed to stabilize the complex formed between the anthraquinones and DNA and was required for antibacterial activity against a number of Gram-positive organisms.

DNA binding, cardiac superoxide production and cytotoxicity of daunomycin analogs.

Pyridoanthraquinones are potent antibacterial agents especially against gram-positive organisms. We tested two major biologic actions of these compounds: DNA intercalation and superoxide (O2-) production in sarcosomes. Using the bathochromic and hypochromic shifts induced by intercalation, followed by Scatchard analysis, we calculated dissociation constants and the number of binding sites per base pair for several analogues. We compared O2- production using cytochrome c reduction. Unsubstituted compounds do not bind to DNA or change its melting temperature (Tm). Placing a morpholino or piperidyl group at C-5 enhances the binding to DNA. The tetracyclic compounds were equipotent at producing O2- and were 20-fold more active than daunomycin. These compounds were unusual in their solid tumor cytotoxicity.

Biotin analogs activate guanylate cyclase.

The sulfur atom in the vitamin biotin has previously been suggested to be essential in biotin's mechanism of action. In a series of investigations on structure-function relationships with biotin analogs not containing the sulfur atom, the biotin analogs, azabiotin, bisnorazabiotin, carbobiotin and isoazabiotin enhanced guanylate cyclase, an enzyme that has recently been demonstrated to be activated by biotin. These analogs increased guanylate cyclase activity two-fold in liver, cerebellum, heart, kidney and colon at 1 microM concentrations. The ED50 for stimulation of guanulate cyclase activity occurred at 0.1 microM for each of the biotin analogs. These data indicate that the sulfur atom is not essential in biotin's activation of guanylate cyclase since these analogs do not contain the sulfur atom. Studies on the ring structure of biotin revealed that even compounds with a single 5-membered ring (2-imidazolidone) could augment guanylate cyclase activity. The guanylate cyclase co-factor manganese was not essential for the enhancement of guanylate cyclase by these agents but a maximal activation of this enzyme by these analogs could not be obtained without manganese present.

New compounds: total synthesis of dl-3a,4,6a-cis-4-(4-carboxybutyl)-hexahydropyrrolo[3,4-d]imidazol-2-one hydrochloride (dl-azabiotin hydrochloride).

The total synthesis of dl-3a,4,6a-cis-4(4-carboxybutyl)-hexahydropyrrolol[3,4-d]imidazol-2-one hydrochloride (dl-azabiotin hydrochloride) was accomplished in a seven-step sequence from 2-ethoxycarbonylazepin-7-one.

Thiocardenolides II: synthesis and pharmacological evaluation of 3beta-thioacetyl-14beta-hydroxy-5beta-card-20(22)-enolide.

The synthesis of a 3beta-thioacetylcardenolide is described. The thioacetate exhibited effects similar to those seen with digitoxigenin acetate on the isolated frog and guinea pig hearts at 1 X 10(-7) dilution. In the intact rat heart, the lethal dose was 5 mg/kg for the thioacetate and 2.5 mg/kg for digitoxigenin acetate. The thioacetate inhibited sodium- and potassium-activated adenosine triphosphatase to the same extent as digitoxigenin, but it was somewhat less inhibitory than digitoxigenin acetate.

Thiocardenolides I: synthesis and biological actions of 3beta-thiocyanato-14beta-hydroxy-5beta-card-20(22)-enolide.

The synthesis of a 3beta-thiocyanatocardenolide is described. The compound exhibited about 0.1 times the cardiotonic effect of digitoxyigenin in the isolated frog heart preparation. At a dosage of 20 mg/kg in the intact rat, it elicited ECG changes similar to those seen with a 10-mg/kg dose of digitoxigenin. Studies also revealed the new cardenolide to be a reversible inhibitor of sodium- and potassium-activated adenosine triphosphatase.

Synthesis of dl-4xi-(2-carboxyethyl)-cis-hexahydropyrrolo-[3,4-d]imidazol-2-one (bisnorazabiotin).

Bisnorazabiotin was synthesized in a six-step sequence from 1,5-dioxo-2-carbethoxypyrrolizidine. It is anticipated that the molecule will serve as a cofactor for biotin-requiring enzymes.

Synthesis of dl-4 xi-(4-carboxybutyl)-5-carbethoxy-cis-hexahydropyrrolo (3,4-d)imidazol-2-one (N-carbethoxyazabiotin).

The total synthesis of dl-4 xi-(4-carboxybutyl)-5-carbethoxy-cis-hexahydropyrrolo[3,4-d]imidazol-2-one (N-carbethoxyazabiotin) by a 16-step sequence, starting from 2-bromo-6-methoxyhexanoic acid, has been accomplished.