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1.
Abstract The well-known tricyclic sesquiterpenoid (?)-sativene, isolated in 1965 from Helminthosporium sativum and shown to possess structure and absolute configuration as indicated by structure 1 3, has been implicated3,4 as an intermediate in the biogenesis of the fungal toxin (?)-helminthosporal (2)5. Two total syntheses of the racemic modification of sativene have been reported6,7. A closely related sesquiterpenoid, (+)-cyclosativene, was isolated from Abies magnifica A. Murr. and was shown to possess structure 3 8,9. The absolute configuration of this material, although not established unambiguously, has been proposed10 as indicated by formula 3. The total synthesis of cyclosativene has not as yet been achieved directly, although it has been obtained indirectly via acid-promoted rearrangement of sativene8,9,11,12. We report herein a total synthesis of (+)-sativene (4) and (+)-cyclosativene (3) via a stereoselective route which unambiguously establishes the absolute configuration of both natural products. 相似文献
2.
The recent publication by Matsumoto1 of a synthesis of Coleon U2(1) prompts us to present our own preparation of this poly-hydroxy diterpene as the tri-O-methyl (12a) and tetra-O-methyl ethers (12b). In a previous communication3 we outlined our approach which is aimed at several similar natural products such as Coleon C4 (1b), Lycoxanthol5 (2), etc. and differs considerably from that of the Japanese group. Formally at least, the two syntheses start with the same material, (+) ferruginol methyl ether 5a. In our case the latter was prepared by recorded methods from methyl O-methyl podocarpate after introducing the iso-propyl sidechain6 (→4), transforming the C.4 methoxycarbonyl residue to a methyl7 (→5a, ferruginol methyl ether) which was oxidised at the benzylic position of the B ring to give sugiol methyl ether 5b. 相似文献
3.
Many antibiotics of the anthracycline family1 possess structures for which 3-methoxyphthalic anhydride (1) would be a suitable synthon2 in a total synthesis. A classic synthesis of (1) has employed 3-nitrophthalic acid3 but, in our hands, proceeded in low overall yield. Recent syntheses have utilized the Diels Alder reaction of dimethyl acetylenedicarboxylate (2) with 1-methoxy-1,3-cyclohexadiene,4 1,4-diacetoxybutadiene,5 2-acetoxyfuran,6 2-methoxyfuran7 or furan8 to obtain 3-hydroxyphthalic acid or a derivative. We now wish to report a convenient Diels-Alder synthesis of (1) from 3-methoxy-2-pyrone (3). 相似文献
4.
Manfred Regitz Wolfgang Rösch Thomas Allspach Ulrich Annen Karsten Blatter Jürgen Fink 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):479-482
Abstract The syntheses of phospholes (7, [3+2]-cycloaddition), bicyclophosphaalkenes (17, [4+2]-cycloaddition), and phosphabenzenes (15, [4+2]-cycloaddition followed by an extrusion process) starting from the phosphaalkynes (4) are described. The 2–Dewar phosphabenzene 18, obtained from the cyclobutadiene 21 and 4 (R =tBu), is the starting material for the synthesis of the valency isomers 19, 20, 22, and 23. 相似文献
5.
A number of total syntheses of (±) - podocarpic acid (i) have been described1 King, King and Topliss2 first identified one of the products from nonstereo-selective cyclization of (4) with polyphosphoric acid as (±)- ethyl-O-methylpodocarpate (2) and correlated that with the corresponding acid (3), prepared in an extremly poor yield (ca 0.4%)3 by Bhattacharyya3, and Haworth and Moore4 by cyclization of (5) with a mixture of sulfuric acid and acetic acid. More recently Mancini, Fringuelli and Taticchi5 prepared (3) (in 4.8% yield) by repeating Howorth1 s cyclization of (4). In continuation of our studies on cyclialky- 相似文献
6.
The acid (-)-2 was converted to the ketone (-)-6. Unsaturated ketone (+)-14 was synthesised from (-)-6. The ketone (+)-7 prepared from the acid (+)-3 on 1,2-ketone transposition, furnished the optical antipode (-)-6. 相似文献
7.
Our continued interest in the total synthesis of natural and unnatural antitumor anthracyclines1 especially the aglycones such as daunomycinone (1)2 and 4-demethoxydaunomycinone (2)3, 11-deoxydaunomycinone (3)4 and 4-demethoxy-11-deoxydaunomycinone (4)5 led us to probe methods of obtaining these products of absolute enantitomeric purity. Earlier it was demonstrated that the AB ring synthon 5 having a chiral centre on fusion with phthalic anhydride gave 4-demethoxy-7-deoxy-daunomycinone (6) with no loss of optical purity6 and the same was further transformed to 2 [7-(S)-9(S)]. 相似文献
8.
As for (S)—homoproline (3) there is a marked discrepancy between the directions of the optical rotation reported by two groups of chemists3,4. Here we wish to communicate novel asymmetric syntheses of (S)—homoproline (3) and (S)—homopipecolic acid (4) carried out in connection with our asymmetric cyclization studies2. We also examined catalytic potentialities of these unnatural β-amino acids in asymmetric aldol cyclization. 相似文献
9.
Tsutomu Tsuchiya Yoshiaki Takahashi Makoto Endo Sumio Umezawa Hamao Umezawa 《Journal of carbohydrate chemistry》2013,32(4):587-611
2′,3′-Dideoxy-2′-fluorokanamycin A (23) was prepared by condensation of 6-azido-4-0-benzoyl-2,3,6-trideoxy-2-fluoro-α-D-ribo-hexopyranosyl bromide (13) and a protected disaccharide (19). Methyl 4,6-0-benzylidene-3-deoxy-β-D-arabino-hexopyranoside (5) prepared from methyl 4,6-0-benzylidene-3-chloro-3-deoxy-β-D-allo-hexopyranoside (1) by oxidation with pyridinium chlorochromate followed by reduction with Na2 S2O4 was fluorinated with the DAST reagent to give methyl 4,6-O-benzylidene-2,3-dideoxy-2-fluoro-β-D-ribo-hexopyranoside (7). Successive treatment of 7 with NBS, NaN3 and SOBr2 gave 13. The structure of the final product (23) was determined by the 1H and 19F and shift-correlated 2D NMR spectra. 相似文献
10.
Abstract Regioselective cleavage of 1,6-anhydro-maltose (1) with periodate and the subsequent recyclization with nitromethane gave 1,6-anhydro-3′-deoxy-3′-nitro-disaccharides (3). Three diastereomers, prepared by benzylidenation of 3, were separated by column chromatography. Each of 4′,6′-O-benzylidene derivatives successively underwent debenzylidenation, reduction of the nitro group, and peracetylation to give 3′-acetamido-3′-deoxy-disaccharide derivatives (7, 8, and 9). The configurations of the 3-amino sugar moietres in 7 (D-gluco), 8 (D-manno) and 9 (D-galacto) were determined on the basis of the 1H NMR data. The main product (7) was further modified to the 6-deoxy-6-nitro derivative. 相似文献
11.
In 1977 Tamaki1 et al have isolated and synthesized2 (Z)-7-nonadecen-ll-one (la) and (Z)-7-eicosen-l1-one (1b) which are active components of the female sex pheromones of the peach fruit moth Carposina niponensis Walsingham, a major economic pest of apple, peach and other fruits of Japan. We report in this communication a practical, convenient and stereospecific route to 1a and 1b. 相似文献
12.
Abstract The reaction of N-phenyliminoketenylidenetriphenylphosphorane [a] (1), with 2-benzylidene-1, 3-indandione (2), 1,2-diphenyl-3,4-pyrazolidenedione (3)and/or 5-benzylidene barbituric acid (4) has been investigated. When ylide 1 was allowed to react with compounds 2, 3 or 4 in THF at ambient temp. the corresponding new pyrano-phosphoranylidenes 5, 6 or 7 were obtained. The elemental microanalyses, IR, 1H NMR, 31P NMR and MS data agree with the structure of the cyclic iminophosphoranes by [4+2]-cycloaddition and exclude 4-membered ring structure by [2+2]-cycloaddition. When the Wittig reaction was carried on the pyrano-phosphoranes 5, 6 or 7 using p-nitrobenzaldehyde, the exocyclic olefins together with triphenylphosphine oxide were isolated. 相似文献
13.
Trichodiene (1), a sesquiterpene hydrocarbon, was isolated from the extract of mycelium of Trichothecium roseum. The structure of trichodiene (1) was elucidated by Nozoe and Machida in 1970 via degradation and spectroscopy.1 Trichodiene (1) has been shown to be the biogenetic precursor of the trichothecane family of sesquiterpenoids as characterized by the cytotoxic fungal metabolite (-)-trichodermin (2).2,3 The structure and absolute stereochemistry of (-)-trichodermin (2) were determined by X-ray diffraction and, therefore, the structure and absolute stereochemistry of trichodiene (1) are now firmly established.4 We wish to report a total synthesis of (±)-trichodiene (1) via previously reported lactone 3.5,6 相似文献
14.
Giovanni Frenza Claudio Fuganti Piero Grasselli Giuseppe Pedrocchi-fantoni 《Journal of carbohydrate chemistry》2013,32(3):225-248
Abstract The erythro and threo chiral C5 methyl ketones (4) and (5), prepared from the (2S, 3R)-methyl diel (1b), were converted into the phenylsulfenimines (6) and (7), which, in turn, on reaction with allyl-magnesiutn bromide, yielded after acid hydrolysis and benzoylation, the diastereoisomeric C8-N-aminodiol derivatives (9) and (11), with threo stereochemistry relative to positions 4 and 5. Ozonolysis of (9) and (11) yielded the l-arabino and l-xylo 3-O-methyl branched aminodeoxysugar derivatives (13) and (15), respectively. Using diallylzinc as the reagent, the diastereoisomeric erythro products (8) and (10) were obtained. The latter materials gave the l-ribo-and l-lyxo-(lL-vancosamine) derivatives (12) and (14) upon oxonolysis. The 1H and 13C NMR spectra of the four isomeric aminodeoxysugar derivatives (12)—(15) were discussed. 相似文献
15.
Trichodiene (1), a sesquiterpene hydrocarbon, was isolated and characterized by Nozoe and Machida in 1970.1 Trichodiene (1) has been shown to be the biogenetic precursor of the trichothecane family of sesquiterpenoids characterized by the cytotoxic fungal metabolite (–)-trichodermin (2).2,3 We recently reported a total synthesis of (±)-trichodiene (1) via lactone 3.4 Now, we wish to report another stereoselective total synthesis of (±)-trichodiene (1) via lactone 3 which is highly regioselective. 相似文献
16.
Both the direct2 and the sensitized3,4 photolyses of (E)-β-ionol (2) have been studied in some detail. In a preliminary publication5 we have indicated that direct photolyses of (E)-β-ionol (2) with λ = 254 nm yields (Z)-retro-γ-ionol (3) as the primary product; upon further irradiation 3 is converted into the corresponding (E)-isomer (4) which rapidly yields the bicyclic alcohol 5. A quantitative study revealed that the photoconversion of (E)-β-ionol with λ = 254 nm to 3 is about 10 times faster than the conversion of 3 into (E)-retro-γ-ionol.6 This rate difference thus allows the photosynthesis of 3. 相似文献
17.
Michael D. Threadgill 《合成通讯》2013,43(12):1101-1105
In a report on the reaction of 2-chloronitrobenzene (1) with diethanolamine (2), Meltsner et al 1 claim that the expected SNAr product, N-(2-nitrophenyl)diethanolamine (3), is not formed; rather that the products are 2,2′-dichloroazobenzene (4), 2-nitrophenol (5), 2-chloroaniline (6) and 4-(2-aminophenyl)morpholine (7). Similar products in which the nitro function is reduced are also reported2 for the corresponding reaction with ethanolamine. In this laboratory, in an attempted preparation of 2,2′-dichloroazobenzene (4) for reference purposes in photochemical studies on the antineoplastic agent 5-(3-azido-4-chlorophenyl)-6-ethyl-pyrimidin-2,4-diamine3, the expected SNAr product (3) was obtained along with other products. 相似文献
18.
α-Dithiophosphates of peracetylated 2-deoxyhexc-pyranoses, 1a, 1b and 2, uhich are easily prepared by addition of organic phosphorodithioic acids to glycais react smoothly with resin-bound 2- and 4-nitrophenoxides to give stereoselectively the respective nitrophenyl 2-deoxy-β-D-hexopyranosides (3, 4, 5 and 6) in high yields. Glycosylation of the 2, 4-dinitro'phenoxide, however, leads with comparable stereoselectivity to 2,4-dinitrophenyl 2-deoxy- α-D-hexopyranosides (7 and 8). Glycosides 3 - 6 are quantitatively deacetylatec by Amberlyst A-26 (OH-), whereas glycosides 7 and 8, under the same reaction conditions undergo splitting of the O-glycosidic bond. 相似文献
19.
o-Carboxyhomomaleanilic acids (5) and o-carboxyhomophthalanilic acids (6) on treatment with sodium acetate-acetic anhydride furnished pyridobenzoxazinones (8) and isoquinolinobenzoxazinones (9) respectively in quantitative yields. Conversion of o-formylhomophthalanilic acid (7) to isocoumarinoquinoline (11) via 2-axo-3(o-carboxyphenyl)quinoline (10) is also described. 相似文献
20.
As a part of our studies in the conversion of triterpenoids into steroids we have reported1 that the Jones oxidation of some triterpenoid hemiacetals (1) gives acyloxy acids (2) instead of the desired 1,5-diketones (3). We now report2 the shortest route yet for the reconstruction of a triterpenoid ring A ketone (4) into a steroidal enone (7) involving as key steps the exhaustive Baeyer-Villiger oxidation3 of triterpenoid ketones (4) into δ-lactones (5) and mild chromium(VI) oxidation of cyclic hemiacetals (1) into diketones (3). 相似文献