Different effects of FK317 on multidrug-resistant tumor in vivo and in vitro

Enantioselective synthesis of 3-substituted 1,2-oxazinanes via organocatalytic intramolecular aza-Michael addition

A highly enantioselective intramolecular 6-exo-trig aza-Michael addition was developed to afford chiral 3-substituted 1,2-oxazinanes in high yields (up to 99% yield) and good enantioselectivities (up to 98/2 er). These reactions were enabled by a quinine-derived primary-tertiary diamine as a catalyst and pentafluoropropionic acid (PFP) as a co-catalyst.

Natural products synthesis: enabling tools to penetrate Nature's secrets of biogenesis and biomechanism

Selected examples from our laboratory of how synthetic technology platforms developed for the total synthesis of several disparate families of natural products was harnessed to penetrate biomechanistic and/or biosynthetic queries is discussed. Unexpected discoveries of biomechanistic reactivity and/or penetrating the biogenesis of naturally occurring substances were made possible through access to substances available only through chemical synthesis. Hypothesis-driven total synthesis programs are emerging as very useful conceptual templates for penetrating and exploiting the inherent reactivity of biologically active natural substances. In many instances, new enabling synthetic technologies were required to be developed. The examples demonstrate the often untapped richness of complex molecule synthesis to provide powerful tools to understand, manipulate and exploit Nature's vast and creative palette of secondary metabolites.

Effects of photochemically activated alkylating agents of the FR900482 family on chromatin

Bioreductive alkylating agents are an important class of clinical antitumor antibiotics that crosslink and monoalkylate DNA. Here, we use a synthetic, photochemically activated derivative of FR400482 to investigate the molecular mechanism of this class of drugs in a biologically relevant context. We find that the organization of DNA into nucleosomes effectively protects it against drug-mediated crosslinking, while permitting monoalkylation. This modification has the potential to lead to the formation of covalent crosslinks between chromatin and nuclear proteins. Using in vitro approaches, we found that interstrand crosslinking of free DNA results in a significant decrease in basal and activated transcription. Finally, crosslinked plasmid DNA is inefficiently assembled into chromatin. Our studies suggest pathways for the clinical effectiveness of this class of reagents.

Cytotoxicity determination without photochemical artifacts

A study was performed to improve cytotoxicity determinations by eliminating flavin-mediated photosensitization from tests with KB cells, NCI-H69 cells, P-glycoprotein expressing KBC5-8 cells, MRP1-expressing H69AR cells, and A240286S human lung adenocarcinoma cells. Growth inhibition by cis-platin, doxorubicin, etoposide, gemcitabine, taxol, vincristine, vinblastine, and vinorelbine was determined under flavin-protecting conditions using flavin-free culture media with fetal bovine serum as the only source of flavins. As compared to conventional tests, the IC50 values determined under flavin-protecting conditions reflected increased apparent drug cytotoxicities, and were flawlessly reproducible. Flavin-mediated photosensitization should, therefore, be strictly eliminated from in vitro experiments involving cytotoxic and other drugs.

A synthetic approach toward the proposed tetracyclic aziridinomitosene derived from FK317

A synthesis of the FK317 derivative 25 is described using internal Michael addition. Tin-lithium exchange of the deuterated stannylaziridine 18 generated the key lithioaziridine intermediate, followed by cyclization and aromatization of the pyrrole ring to give 7. Ester reduction from 7 to 23 was effected via temporary aldehyde protection as the silylimidazole adduct 22, and conversion to the carbamate 25 was carried out using FmocNCO and FMOC cleavage. Structure 25 is the N-trityl-protected derivative of the proposed intermediate from bioactivation of FK317 that is responsible for DNA cross-linking. Attempted nitrogen deprotection of 25 using MsOH/i-Pr(3)SiH resulted in replacement of the C(10) carbamate by hydride. Deprotection of the more stable 21 gave the desired aziridine 26.

A Concise Total Synthesis of (+)-FR900482 and (+)-FR66979

The concise, enantioselective total synthesis of the potent antitumor antibiotics (+)-FR900482 and (+)-FR66979 are described. Sharpless asymmetric epoxidation technology has been deployed to construct the optically active aziridine-containing fragment that is joined to the aromatic moiety in a highly convergent manner. Dimethyldioxirane effects the remarkable one-step deprotection/oxidative cyclization of an eight-membered ring amino-ketone to the unique hydroxylamine hemiketal ring system that is a distinctive structural motif of FR900482. This reaction has been exploited in a concise 33-step enantioselective total synthesis of FR900482.

Synthesis and DNA cross-linking of a phototriggered FR900482 mitosene progenitor

[reaction: see text] The synthesis and biochemical reactivity of the first photoactivated mitosene-based DNA interstrand cross-linking agent is described.

Effects of FK317, a novel anti-cancer agent, on survival of mice bearing B16BL6 melanoma and Lewis lung carcinoma

The effects of FK317 (11-acetyl-8-carbamoyloxymethyl-4-formyl-6-methoxy-14- oxa-1,11-diazatraacylo[7.4.1.0(2.7).0(10.2)]-tetradeca-2,4,6-trien-9-yl acetate), a novel anti-cancer agent, and mitomycin C (MMC) on survival time of mice bearing B16BL6 melanoma and Lewis lung carcinoma (LLC), induced by intravenous inoculation of the tumor, were investigated. Treatment with FK317 resulted in a significant prolongation of survival time in both tumor models. Four of ten mice bearing B16BL6 were disease-free following FK317 treatment. In contrast, MMC was not effective in prolonging survival time. Overall, this study demonstrated that FK317 shows more potent survival extension in mice bearing B16BL6 and LLC than MMC, suggesting that FK317 may have therapeutic utility for cancer chemotherapy.

Differential effects of FR900482 and FK317 on apoptosis, IL-2 gene expression, and induction of vascular leak syndrome

Vascular leak syndrome (VLS) is a harmful side effect that resulted in withdrawal of the antitumor drug FR900482, but not FK317, from clinical trials. Here we present chromatin immunoprecipitation data showing that FK317, like FR900482, crosslinks minor-groove binding proteins to DNA in vivo. However, these drugs differ in how they induce cell death. We demonstrate that, whereas FR900482 induces necrosis, FK317 induces a necrosis-to-apoptosis switch that is drug concentration dependent. Northern blot analyses of drug-treated cells suggest that this "switch" is mediated, at least in part, by modulation of the expression levels of Bcl-2. Additionally, FR900482, in contrast to FK317, induces the expression of known elicitors of both Bcl-2 gene expression and VLS. These findings provide plausible explanations for why these structurally similar drugs have different biological effects, especially with respect to VLS.

Observations on the covalent cross-linking of the binding domain (BD) of the high mobility group I/Y (HMG I/Y) proteins to DNA by FR66979

FR66979, a drug closely related to the mitomycin C class of antitumor antibiotics, is shown to covalently cross-link DNA to the DNA-binding domain of the High Mobility Group I/Y (HMG I/Y) DNA-binding proteins in the minor groove.

FK317, a novel substituted dihydrobenzoxazine, exhibits potent antitumor activity against human tumor xenografts in nude mice

The antitumor effects of FK317, a novel substituted dihydrobenzoxazine, were evaluated using human tumor xenografts (small cell lung cancer, non-small cell lung cancer, stomach cancer, colon cancer, pancreatic cancer, breast cancer, cervical cancer and ovarian cancer). Tumor growth-inhibitory effects and the effective dose-range of FK317 were much stronger and broader, respectively, than those of reference drugs such as mitomycin C, adriamycin, cisplatin, taxol and irinotecan. Furthermore, the body weight decrease and myelosuppression in FK317-treated mice were less than in the animals given any of the reference drugs. To explain this tumor selectivity, the distribution of FK317 was investigated after dosing tumor-bearing mice with the 14C-labelled compound. The concentration of FK317 in tumor tissues was relatively low, and long tumor retention was not observed. However, thin-layer chromatographic separation revealed that the radioactivity in the tumor resided mainly in strongly cytotoxic metabolites, while that in other tissues resided mainly in non-cytotoxic metabolites. These results suggest that FK317 shows strong antitumor activity without side effects, and one reason for this is its specific metabolite pattern. FK317 is now undergoing phase I clinical trials.