Structure-activity relationships of sparsomycin and its analogs. Inhibition of peptide bond formation in cell-free systems and of L1210 and bacterial cell growth

Abstract

The biological activity of 14 analogues of sparsomycin (1) was studied in cell-free systems of Escherichia coli, Saccharomyces cerevisiae, and Sulfolobus solfataricus by measuring the inhibition of protein synthesis. The inhibition of L1210 colony formation in soft agar and bacterial cell growth in solid as well as in liquid medium was also examined. Each analogue possesses not more than two structural modifications of the sparsomycin molecule. This enabled us to determine unambiguously several structural and stereochemical features that are required for an optimal biological activity in these assays. Sparsomycin, having the SCRS chirality, is the most potent of the four possible stereoisomers. The results obtained with compounds 5-7 indicate that the presence of an oxygen atom on the S (alpha) atom is essential. Substitution of the bivalent sulfur atom by a CH2 group (10) or of the SCH3 moiety by a Cl atom (12) affects the activity of the molecule partially. Compound 12 is surprisingly active against intact cells. Substitution of the C(6)-CH3 group by a H(14) reduces the activity of the molecule. Isomerization of the trans double bond into the cis double bond yields cis-sparsomycin (15), which is inactive. The hydrophobic derivatives 8, 9, and 11 are considerably more active than sparsomycin; thus the ribosomal binding site for sparsomycin may have a hydrophobic character.

Biochemical and kinetic characteristics of the interaction of the antitumor antibiotic sparsomycin with prokaryotic and eukaryotic ribosomes

“…¡Sparsomycin1 (Figure 1) is a broad-spectrum antibiotic that inhibits protein synthesis by interacting with the ribosome at the peptidyl transferase center, blocking peptide bond formation [see Ottenheijm et al (1986) for a review on sparsomycin] . Lately, the preparation of sparsomycin derivatives considerably more active than the original drug (van den Broek et al, 1987(van den Broek et al, , 1989-some of which have produced promising results in ongoing clinical tests (Zylicz, 1988)-has stirred up new interest in this drug as an antitumor agent. Sparsomycin 0006-2960/91 /0430-9642S02.50/0 is also of considerable interest from an even more basic point of view since its strong inhibitory activity on all cell types, including the highly resistant archaebacteria (Cammarano et al, 1985), indicates the existance of a highly conserved target for drug action in all ribosomes.…”

Sparsomycin – a Review and Re-assessment

“…11,[37][38][39][40][41] These efforts were extended to the development of synthetic routes for analogs for additional biological assessment. [41][42][43][44][45][46][47] Two groups published their syntheses of the unnatural RC diastereomer of 1 almost simultaneously, 37,38 in which a convergent approach assembled an acid and an amine to form the amide bond of 1. Commencing with 6-methyluracil (12), the requisite acrylic acid 13 37 was formed in four steps through hydroxymethylation at C-5, oxidation to the aldehyde, followed by a Wittig condensation with Ph3P=CHCO2C2H5, and base hydrolysis.…”

“…52 When the four isomers of 1 were examined in antibacterial, yeast inhibition, and L1210 colony forming assays, the SCRS-configuration of natural 1 was the most active compound. 53 In addition, substituting the CH2SMe group at S1 with either -C3H7 or -Cl reduced activity, and isomerization of the double bond from E-to Zeliminated activity, as did removing the sulfoxide oxygen at S1. However, the S2-octyl, -benzyl, and -Et analogs of 1 were more active in the L1210 colony forming assay.…”

“…However, the S2-octyl, -benzyl, and -Et analogs of 1 were more active in the L1210 colony forming assay. 53 Interestingly, against the L5178Y leukemia cell line analogs lacking any sulfur and with a more hydrophobic pyrimidine ring were highly cytotoxic, e.g., 57, although ED50 values were not determined. 54 Broad in vivo antitumor testing revealed that 1 was weakly active or inactive, whereas deshydroxy-sparsomycin (58), n-pentyl-sparsomycin (59), and ethyl-deshydroxy-sparsomycin (60) were significantly active in the L1210 and renal cell sarcoma models.…”

Mechanism of action of sparsomycin in protein synthesis

“…Sparsomycin is a sulfoxide-containing antibiotic that inhibits protein synthesis in sensitive prokaryotic and eukaryotic systems (Ottenheijm et al, 1986;Cundliffe, 1981). It has also been investigated as a potential antitumor agent and is of current interest in several laboratories (van den Broek et al, 1987(van den Broek et al, ,1989aFlynn & Ash 1990; Lazaro et al, 1991). There is general agreement that sparsomycin acts on the large ribosomal subunit and inhibits peptide bond formation.…”