115706-57-5Relevant academic research and scientific papers
General approach to anthrapyran antibiotics exemplified by the synthesis of rac-γ-indomycinone
Krohn, Karsten,Tran-Thien, Hoan Trang,Ahmed, Ishtiaq
, p. 2223 - 2225 (2011)
A new general route to the anthrapyran antibiotics is presented, which allows the attachment of various branched side chains. A key step is the Baker-Venkataraman rearrangement of the propionate 9 to the diketone 10. Acid-catalyzed cyclization gives the ethyl-branched anthrapyranone 11, serving as the starting material for further side-chain elongation. For example, the ethyl-substituted anthrapyranones 12a,b,c, the corresponding bromides 13b,c, the phosphonium salts 14b,c, the olefins 22a,c, and the epoxides 23a,c are prepared by starting from 11. A first example demonstrating the potential of this route is the synthesis of the naturally occurring γ-indomycinone (24b), prepared bycuprate-mediated opening of the epoxide 23a. A general route to the anthrapyran antibiotics is presented, which allows the attachment of various branched side chains. In a first example, an ethyl-branched anthrapyranone, prepared in a Baker-Venkataraman rearrangement, was used to obtain a 1-methylvinyl-substituted anthrapyranone that was transformed into rac-indomycinone via an intermediate epoxide in a cuprate-mediated epoxide opening. Copyright
Total synthesis of silyl-protected early intermediates of polyketide biosynthesis
Krohn, Karsten,Vidal, Anne,Tran-Thien, Hoan Trang,Floerke, Ulrich,Bechthold, Andreas,Dujardin, Gilles,Green, Ivan
, p. 3080 - 3092 (2010)
The ketal-or dithioketal-protected isocoumarins 15-18 gave the corresponding 1-naphthols 21-26 in their reactions with the acetoacetate (10) or pentane-2, 4-dione (19) dianions and the acetone monoanion. Subjection of the dithioketal-protected ester 28 to
Total synthesis of aklanonic acid and derivatives by Baker-Venkataraman rearrangement
Krohn, Karsten,Roemer, Ernst,Top, Michael
, p. 271 - 277 (2007/10/03)
Aklanonic acid (1) and the derivatives 2 and 15a-f were prepared by Baker-Venkataraman rearrangement of the corresponding ortho-acetyl anthraquinone esters 13a-e and 14 using lithium hydride in THF. VCH Verlagsgesellschaft mbH, 1996.
Biomimetic Syntheses of Pretetramides. 2. A Synthetic Route Based on a Preformed D Ring
Harris, Thomas M.,Harris, Constance M.,Oster, Timothy A.,Brown, Larry E.,Lee, John Y.-C.
, p. 6180 - 6186 (2007/10/02)
A route to pretetramides has been developed on the basis of tandem condensations of homophthalate esters with the dianion of methyl acetoacetate to give aromatic bis(diketo esters), which cyclize spontaneously to anthracene diesters.A further condensation of one of the ester groups with acetamide synthons gives anthracene ester-keto amides, which can be cyclized to naphthacenecarboxamides.By this technique dimethyl 3-methoxyhomophthalate (2b) was condensed with the dilithium salt of methyl acetoacetate to give anthracene diester (4b).Protection of the hydroxyl groups followed by treatment with the dilithium salt of N-(trimethylsilyl)acetamide gave anthracene ester-keto amide 6, which cyclized to pretetramide (1) on treatment with HBr in acetic acid.The procedure for synthesis of pretetramide was modified to permit separate addition of the ketide chains.By use of the aliphatic mono ester (7b) of 3-methoxyhomophthalic acid, chain extension was brought about at the aliphatic carboxyl group by condensation with the dilithium salt of tert-butyl acetoacetate.This product was cyclized to isocoumarin 9b by treatment with acetic anhydride.Completion of the backbone was achieved in a single condensation by treatment of 9b with trianion 18 of 3,5-dioxohexanenitrile (prepared from the nitrile or indirectly by cleavage of isoxazole 17 with LDA) to give anthrone 32.A variety of other condensations of the trianion 18 was performed with electrophiles to demonstrate the utility of the reagent.The synthesis of pretetramide from anthrone 32 was completed by treatment with HI/phenol.
