- Brasiliquinones A-C, new cytotoxic benz[a]anthraquinones with an ethyl group at C-3 from actinomycete Nocardia brasiliensis
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Three new cytotoxic benz[a]anthraquinones with an ethyl group at C-3, brasiliquinones A-C 1-3, have been isolated from the actinomycete Nocardia brasiliensis IFM 0089, and their structures elucidated on the basis of spectroscopic data and by chemical means. Brasiliquinone A 1 is the first benz[a]anthraquinone possessing ristosamine as an O-glycoside moiety, while brasiliquinones B 2 and C 3 correspond to the aglycone of 1 and the 8-O-methyl derivative of 2, respectively.
- Tsuda, Masashi,Sato, Hiroyasu,Tanaka, Yasushi,Yazawa, Katsukiyo,Mikami, Yuzuru,Sasaki, Takuma,Kobayashi, Jun'ichi
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- Total synthesis of both enantiomers of Daunosamine and Ristosamine
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Efficient, enantioselective syntheses of the title 3-amino-2,3,6-trideoxyhexoses from non-carbohydrate precursors, (S)- and (R)-1-(2-furyl)ethanol, readily available by enzyme-mediated kinetic resolution, are described. Furan compound (S)-3 was converted
- Szechner,Achmatowicz,Badowska-Roslonek
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p. 1133 - 1141
(2007/10/03)
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- 4-Isopropyl-2-oxazolin-5-one anion as masked umpoled synthon for both formyl and hydroxycarbonyl anions: Generation, reactivity and synthetic applications
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The anion of the title compound, simply generated in the presence of catalytic amount of triethylamine, reacts with both common electrophilic olefins and aldehydes to give moderate to good yield of Michael or aldol adducts respectively. Mild acid treatment of these adducts at ambient temperature serves to demask the aldehyde function, allowing one to consider the anion of 1 as a nucleophilic acylating equivalent of formaldehyde. On the other hand, the same anion of 1 may act as a masked umpoled synthon for a hydroxycarbonyl anion since its aldol adducts with aldehydes undersent concomitant isomerization and ring cleavage under mild basic conditions producing dipeptides which could be hydrolyzed to give the corresponding carboxylic acids. Synthetic applications of this chemistry in the area of sugar, aminosugar and non-proteinogenic aminoacid derivatives are discussed.
- Barco, Achille,Benetti, Simonetta,De Risi, Carmela,Pollini, Gian P.,Spalluto, Giampiero,Zanirato, Vinicio
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p. 4719 - 4734
(2007/10/03)
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- The total synthesis of L-daunosamine
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N,O-Dibenzyl-N-tert-butoxycarbonyl-L-homoserinal (7), obtained from L-aspartic acid, reacts with vinylmagnesium chloride to afford with high stereoselectivity compound 6 which is subsequently transformed into the derivative of L
- Jurczak, Janusz,Kozak, Janusz,Golebiowski, Adam
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p. 4231 - 4238
(2007/10/02)
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- A DIHYDROISOXAZOLE-BASED ROUTE TO 2,3,6-TRIDEOXY-3-AMINOHEXOSE DERIVATIVES
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Acosamine and ristosamine derivatives were prepared via stereoselective reductive cleavage reactions of a benzylidenated dihydroisoxazolyl diol; the diol was prepared from 3-nitro-4,5-dihydroisoxazole via sequential propynylation, Lindlar reduction, and c
- Wade, Peter A.,Appa Rao, J.,Bereznak, James F.,Yuan, C.-K.
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p. 5969 - 5972
(2007/10/02)
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- SYNTHESIS OF (L)-DAUNOSAMINE AND RELATED AMINO SUGARS
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1-(2-Furyl)ethanol (6) has been converted into methyl (+/-)-daunosaminide (1) and methyl (+/-)-ristosaminide (3) by use of an intramolecular cyclisation of a trichloroacetimidate group. (+/-)-Daunosamine (1) has been obtained more directly from the alcohol (10) by use of a modified Mitsunobu reaction; the scope of the latter reaction has been explored using cyclohex-2-en-1-ol as a model substrate.Asymmetric reduction of 2-acetylfuran (5) has given (S)-1-(2-furyl)ethanol (46) in good enantiomeric excess, thus providing a short route to the L-enantiomers of the amino sugars (1), (2), and (3) from a cheap, non-carbohydrate precursor.
- Sammes, Peter G.,Thetford, Dean
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p. 111 - 124
(2007/10/02)
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- SYNTHESIS OF N-TRIFLUOROACETYL-L-ACOSAMINE, N-TRIFLUOROACETYL-L-DAUNOSAMINE, AND THEIR 1-THIO ANALOGS
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A simple and efficient route to N-trifluoroacetyl-L-acosamine (13), N-trifluoroacetyl-L-daunosamine (12), and their 1-thio analogues (18 and 20) is described.Stereoselective reduction of oxime 5 with borane, followed by trifluoroacetylation resulted in the arabino methyl glycoside (8), which, on mild acid hydrolysis gave N-trifluoroacetyl-L-acosamine (13) in an overall yield of 33percent, based on L-rhamnal (1).Upon oxidation of the C-4 hydroxyl group and stereoselective reduction of the resulting ketone 11, compound 8 of L-arabino configuration was converted into N-trifluoroacetyl-L-daunosamine (12) in a one-flask sequence with an overall yield of 28percent calculated for 1.Benzyl 1-thio-N-trifluoroacetyl-α-L-acosaminide (18) was synthesized from enone 2 on Michael-type addition of phenylmethanethiol, followed by oximation, stereoselective reduction with borane and subsequent trifluoroacetylation. 4-O-Acetyl-1-S-acetyl-N-trifluoroacetyl-1-thio-β-L-daunosamine 20 was prepared from 12 via the corresponding glycosyl chloride derivative.
- Pelyvas, Istvan,Hasegawa, Akira,Whistler, Roy L.
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p. 193 - 204
(2007/10/02)
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- Stereocontrolled routes to cis-hydroxyamino sugars, Part VII: Synthesis of daunosamine and ristosamine.
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The nitrogen of an allylic amine can serve as the fulcrum for stereocontrolled delivery of oxygen to an adjacent trigonal site, and cis-hydroxyamino sugars can thus be prepared. Methods for achieving the complementary procedure, namely, control of the delivery of nitrogen to an adjacent site by an allylic oxygen, are described. For example, treatment of methyl 2,3,6-trideoxy-alpha-L-erythro-hex-2-enopyranoside with trichloroacetonitrile gave an imidate ester which reacted with iodonium dicollidine perchlorate to give 2-trichloromethyl-(methyl 2,3,4,6-tetradeoxy-2-iodo-alpha-L-altropyranosido)-[3,4-d]-2-oxazo line. Exhaustive reductive dehalogenation of this product followed by hydrolysis led to methyl N-acetyl-alpha-L-ristosaminide. An analogous series of reactions was used to prepare the corresponding daunosaminide.
- Pauls,Fraser-Reid
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p. 111 - 119
(2007/10/02)
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