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A convenient protocol for the β-stereoselective synthesis of 2-deoxy-C-arylglycosides has been developed. This reaction takes place in one step by using I2/Et3SiH to activate a glycosyl acetate to generate a glycosyl iodide intermediate in situ, which is captured by a naphthol; this is followed by a Fries-like O-to-C glycoside rearrangement to afford a β-C-aryl glycoside selectively. The approach is applicable to a wide range of naphthol moieties, and its utility was demonstrated in syntheses of 5-aza analogues of aquayamycin.

Total syntheses of aquayamycin (3) and a number of analogues of angucycline antitumor antibiotic derhodinosylurdamycin A bearing various 2-deoxy sugar subunits (4–7) have been achieved. These molecules (3–7) were synthesized based on a convergent strategy for the synthesis of derhodinosylurdamycin A (2) previously reported from our group. In particular, our recently developed mild cationic gold-catalyzed glycosylation with S-but-3-ynyl thioglycoside donors was employed for the synthesis of analogues (6 and 7) bearing disaccharide subunits containing α-L-olivoside and α-L-olioside moiety, respectively. Aquayamycin (3), analogues (4–7), and our previously synthesized derhodinosylurdamycin A (2) were then submitted to the Development Therapeutics Program of the National Cancer Institute of National Institutes of Health for the NCI-60 Human Tumor Cell Lines Screening using standard protocols. It was found that derhodinosylurdamycin A (2), aquayamycin (3), and three other analogues (5–7) bearing sugar subunits did not show significant antiproliferative activity against those cancer cell lines. Interestingly, analogue (4) bearing no sugar subunit demonstrates good potential for growth inhibition and cytotoxic activity against a variety of human cancer cell lines.

v GENERAL INTRODUCTION 1 Dissertation Organization 1 CHAPTER 1. FURAN SYNTHESIS VIA A 4 + 1 RING BUILDING STRATEGYAN APPROACH TO 2,4-DL\CYLFURANS 2 Introduction 2 Results and Discussion 6 Conclusion 10 Experiments 10 References 14 CHAPTER 2. TOTAL SYNTHESIS OF HIBISCONE C 17 Introduction 17 Results and Discussion 19 Conclusion 26 Experiments 26 References 31 CHAPTER 3. SYNTHETIC APPROACH TO NATURAL ANALOGUES OF HALENAQUINONE 32 Introduction 32 Results and Discussion 41 Conclusion 51 Experiments 52 References 57 CHAPTER 4. A SYNTHETIC APPROACH TO AQUAYAMYCIN 60 Introduction 60 Results and Discussion 68 Conclusion 74 Experiments 74 References 79 CHAPTERS. GENERAL CONCLUSION ACKNOWLEDGEMENTS 82 83

An efficient and practical total synthesis of aquayamycin has been accomplished. The highly oxidized and stereochemically complex tetracyclic ring system was constructed using three key reactions: 1) highly diastereoselective 1,2-addition of C-glycosyl naphthyllithium to a cyclic ketone, 2) indium-mediated site-selective allylation-rearrangement sequence of naphthoquinone, and 3) diastereoselective intramolecular pinacol coupling. This synthetic strategy offers a novel and efficient pathway to prepare aquayamycin-type angucycline antibiotics.

Vineomycin A1 (1) and B2 (2) were isolated from the culture broth of marine actinomycete Streptomyces sp. A6H. Five hydrolysis products were obtained by rational hydrolysis and methanolysis of the fermentation extract. Their structures were characterised as aquayamycin (3), vineomycinone B2 (4), 9-C-D-olivosyltetrangulol (5), 7-O-methylgaltamycinone (6) and vineomycinone B2 methyl ester (7). In addition to these compounds, two ester derivatives, vineolactone A (8) and vineomycinone B2 benzyl ester (9) of compound 4 were generated semisynthetically. Compound 6 is a new analogue of galtamycinone, while compounds 8 and 9 are new members of vineomycins. Cytotoxic activities and antimicrobial activities were determined for all compounds. The results indicate that only compound 1 showed significant activities with IC50 value of 0.34 μM against H1975 and MIC value of 4 μg/mL against Staphylococcus aureus.

The λ3-iodane [bis(trifluoroacetoxy)]iodobenzene (BTI)-mediated oxidative dearomatization of 2-alkoxyarenols with soft external carbon-based nucleophiles constitutes a rapid access to highly functionalized naphthoid cyclohexa-2,4-dienones. These synthons can serve as valuable intermediates in the construction of the angularly-oxygenated benz[a]naphthalene ABC ring system of aquayamycin- and SS-228Y-type antibiotic angucyclinones, and analogues thereof. This methodology led to the elaboration of five-membered A ring-containing analogues of this ABC tricyclic unit. In addition, the BTI-mediated oxidative activation of 2-methylnaphthol can be exploited to prepare menadione (i.e. vitamin K3), known to induce apoptosis and autoschizis, a novel type of cancer cell death.

The first synthesis of the racemic 8-deoxy WP 3688-2 angucycline antibiotic (3), with characteristic cis-hydroxy groups at C-4 a and C-12 b, is reported. Key steps involve the coupling, mediated by samarium diiodide, of the bicyclic trione 37 to the tricyclic cis-diol 39. Biomimetic aldol cyclization of the corresponding dione 41 gave a mixture of the tetracyclic cis- and trans-3,4 a-diols 42 and 43, which were oxidized by cerium ammonium nitrate to the quinones 45 and 3. The synthetic compounds 45 and 3 corresponded in configuration to the angucycline antibiotics aquayamicin (1) and WP 3688-2 (2), respectively.

An efficient synthetic route to 3-(phenylsulfonyl)phthalides possessing a β- C -olivoside was developed by exploiting the regioselective [2+2] cycloaddition of benzyne with ketene silyl acetal. The compounds are useful in the total synthesis of the angucyclines, including aquayamycin.

A highly oxygen-functionalized cyclohexenone 2 , the AB ring fragment for the aquayamycin synthesis, was efficiently synthesized via stereoselective addition of allylzinc bromide to ketone 3a which, in turn, was available from the optically pure cyclohexane 1,2,3-triol derivative 5 .

The synthesis of novel aquayamycin-derived angucycline antibiotics 13a–d has been achieved. Glycosylation of aquayamycin (6) using 2-selenoglycosyl acetate 7 as glycosyl donor proceeded in excellent yield but attempts to reductively remove the selenyl group led to rearrangement or further aromatization of the aglycon. As a consequence of these results, it became possible to prepare urdamycinone B (10) starting from aquayamycin (6). In addition, silyl protected d -olivals 12a,b were attached to the C-glycoside domain of aquayamycin (6) under protic conditions. As expected, the hydroxy and phenol groups of the benz[a]anthracene framework of 6 did not react under the glycosylation conditions employed. Stepwise removal of the silyl protecting group starting with tetrabutyl ammonium fluoride followed by use of the HF/pyridine complex suppressed a possible rearrangement of the aglycon and successfully terminated the sequence. The new angucycline-antibiotics 13a and 13b are some of the most potent xanthine oxidase inhibitors known and show cytotoxic activity with ED50-values in the range of 12.6–2.9×10−6 M

The first total synthesis of aquayamycin (1) has been accomplished. The crucial steps include (1) the Hauser reaction between 3-(phenylsulfonyl)phthalide 3 and cyclohexenone 4 to make up the linear BCD tricycle, and (2) the intramolecular pinacol coupling of keto aldehyde 7 to the full tetracyclic framework.

An approach to the ABC ring system of aquayamycin which incorporates a selectively protected cis-diol unit is described. The key step is an intramolecular addition of the anion of a protected cyanohydrin to a ketone.

The angucycline group of antibiotics is one of the largest groups of polycyclic aromatic polyketides, rich in chemical scaffolds and biological activities, predominantly anticancer and antibacterial.1–3 Saquayamycins,4–8 urdamycins,9–17 and landomycins,18–24 are well known angucycline antitumor antibiotics. The structures of both saquayamycins and urdamycins contain the same aquayamycin (17)25–27 as aglycone with the C-glycosidic sugar D-olivose attached at C-9 of the angucycline chromophore. So far, seven saquayamycin analogues were reported from Streptomyces spp. Saquayamycins differ from urdamycins by their saccharide patterns, which are attached at C-9 and C-3 positions in the saquayamycins, but at C-9- and C-12b-positions in urdamycins. Saquayamycins A-D (7–10) were first isolated from Streptomyces nodosus MH190-16F3 and were reported as platelet aggregation inhibitors.4 Saquayamycins A-B (7–8) contain three different O-glycosidically linked deoxysugars, L-rhodinose, L-aculose, and L-cinerulose (only in saquayamycin B). Saquayamycin A (7) was reported to be unstable to acid, and even contact with silica gel led to its conversion to saquayamycin B (8). Saquayamycins A1 (11), B1 (6), and C1 (12) were generated by partial acid hydrolysis of saquayamycins A-C (7–9), respectively.4 The two isomers, saquayamycins E (13) and F (14) were produced by Actinomyces strain MK290-AF1 and reported to inhibit the FPTase from bovine brain with IC50 values of 1.8 and 2.0 μM, respectively.5 They differ slightly from the saquayamycins A (7) and C (9) with respect to their sugar moieties. The saquayamycin analogue A-7884 (16) was isolated from the Streptomyces sp. #AM1699; it has a trisaccharide side chain connected at C-9, which contains an L-rhodinose sugar moiety between the first sugar, a C-glycosidic bound D-olivose, and L-aculose of saquayamycin A1 (11).28 Compound 16 showed inhibitory activity in the inducible nitric oxide synthase (iNOS) assay with IC50 values of 43.5 μM, better than saquayamycin A1 (11; IC50 values of 101.2 μM).28 Recently, the largest saquayamycin analogue, saquayamycin Z (15), was reported from Micromonospora sp. strain Tu6368.6 Saquayamycin Z (15) contains tetra- and pentasaccharide side chains linked at C-3- and C-9-positions of the benz[a]anthracene core. The tetrasaccharide side chain of saquayamycin Z (15) is striking due to the presence of an L-oliose, which is not a usual sugar constituent of the angucyclines.6, 29 Very recently, Ren et al., reported three novel members of the angucycline family named N05WA963 A, B and D, with the same aglycones as in the moromycins A (18) and B (19), except for an additional methoxy group attached at C-5.30 N05WA963 A, B and D were reported to have antiproliferative effects on a panel of cancer cell lines such as SW620 (colon cancer), K-562 (chronic myelogeneous leukemia), MDA-MB-231 (estrogen receptor negative breast cancer), YES-4 (esophageal cancer), T-98 and U251SP (both glioblastomae). To study the structure-activity relationship (SAR) of this saquayamycin group of antibiotics, we looked for further saquayamycin analogues produced by Streptomyces sp. K40-1, the strain earlier reported as the producer of moromycins A-B (18–19).7 The saccharide attachments in moromycins A (18) and B (19) are like those of saquayamycins B (8) and B1 (6), respectively, however, their tetracyclic angucyclinone core has an aromatic ring B, and thus no angular hydroxy groups at C-4a and C-12b positions. We found five new metabolites, designated as saquayamycins G-K (1–5), produced by repeated fermentations of the same strain, along with saquayamycin B1 (6), which was previously not described as a natural product, and known saquayamycins. Two of the new angucyclines, saquayamycins H (2) and I (3), bear the unusual aminosugar rednose, which was found for the first time in an angucycline compound. Aminosugar-containing angucyclines are very rare, and previously only three examples had been reported, namely the marmycins A and B,31, 32 and mayamycin.33 The marmycins contain an unusual branched and doubly (C- and N)-linked aminosugar, 3-epi-, 4-epi-vancosamine, and mayamycin contains a unique C-glycosidically linked aminosugar, N-demethylangolosamine, attached at the C-5-position of the benz[a]anthracenone core.

In order to investigate mid and early biosynthetic steps of angucycline group antibiotics, approximately 400 mutants ofthe urdamycin producer Streptomyces fradiae (strain Tu 2717) were prepared, of which ca. 10% were selected for further investigations. The selection criterion, i.e., the consideration of only pale-colored metabolite-producing blocked mutants, yielded several mutants whose block was in close proximity to the known late-stage biosynthetic steps

An efficient synthetic route to 3-(phenylsulfonyl)phthalides possessing a β- C -olivoside was developed by exploiting the regioselective [2+2] cycloaddition of benzyne with ketene silyl acetal. The compounds are useful in the total synthesis of the angucyclines, including aquayamycin.

Molecular oxygen-based procedures for the stereocontrolled introduction of oxygen functionality present in the antitumor antibiotics aquayamycin (1) and SF 2315B (2) are described

Experiments with 18 O 2 and [1- 13 C, 18 O 2 ]acetate determined the biosynthetic origin of the oxygen atoms of aquayamycin (1), which is the aglycon moiety of the urdamycins A (2, kerriamycin B) and G (3, OM 4842) and the most frequently occuring aglycon among the angucyclines

CAN oxidation (in two steps) of the hydroquinone dimethyl ether 1 gave a hydroxylation product 4 , identical in substitution pattern and relative stereochemistry with the quinoid part of urdamycinone F ( 6 ).

The structure of a new antibiotic, aquayamycin, has been established as derivative of benze[ a ]-anthracene by spectroscopic and degradative experiments.