- De novo synthesis of novel bacterial monosaccharide fusaminic acid
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Fusobacterium nucleatum is an oral bacteria related to various types of diseases. As Gram-negative bacteria, lipopolysaccharide (LPS) of Fusobacterium nucleatum could be a potential virulence factor. Recently, the structure of O-antigen in LPS of Fusobact
- Wei, Ruohan,Liu, Han,Li, Xuechen
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p. 420 - 431
(2019/03/29)
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- Acyclic 1,4-Stereocontrol via the Allylic Diazene Rearrangement: Development, Applications, and the Essential Role of Kinetic e Stereoselectivity in Tosylhydrazone Formation
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We report full details of a method for 1,3-reductive transposition of α-alkoxy-α,β-unsaturated hydrazones to provide E-alkenes with high 1,4-stereocontrol between the two respective allylic stereocenters. The process couples a chelation-controlled reduction of the hydrazone with an in situ allylic strain controlled retro-ene reaction of an allyl diazene, i.e., an allylic diazene rearrangement. Such stereotriads are frequently observed motifs in natural products. We observed a fortuitous kinetic preference for the E-hydrazone geometry during the hydrazonation reaction, as only the E-isomers could undergo chelation-controlled reduction.
- Shrestha, Maha L.,Qi, Wei,McIntosh, Matthias C.
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p. 8359 - 8370
(2017/08/23)
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- Additions of Organomagnesium Halides to α-Alkoxy Ketones: Revision of the Chelation-Control Model
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The chelation-control model explains the high diastereoselectivity obtained in additions of organometallic nucleophiles to α-alkoxy ketones but fails for reactions of allylmagnesium halides. Low diastereoselectivity in ethereal solvents results from no chelation-induced rate acceleration. Additions of allylmagnesium bromide to carbonyl compounds are diastereoselective using CH2Cl2 as the solvent even though rate acceleration is still absent. Stereoselectivity likely arises from the predominance of the chelated form in solution. Therefore, a revised chelation-control model is proposed.
- Read, Jacquelyne A.,Yang, Yingying,Woerpel
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p. 3346 - 3349
(2017/07/13)
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- (S) - 2-benzyloxy-3-pentanone method for the preparation of
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The invention discloses a preparation method of (S)-2- benzyloxy-3-pentanone. The preparation method comprises the steps as follows: (1), L-methyl lactate or L-ethyl lactate is taken as a raw material and compounded with N, O-dimethylhydroxylamine hydroch
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Paragraph 0024; 0035; 0038
(2017/02/09)
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- Acyclic 1,4-stereocontrol via reductive 1,3-transpositions
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(Chemical Equation Presented) One-pot reduction/allylic diazene rearrangement of lactic acid- and mandelic acid-derived α,β- unsaturated tosyl hydrazones leads to 1,4-syn-or 1,4-anti-E-2-alkenyl arrays in high yield and diastereoselectivity. Either the syn or the anti diastereomer can be prepared by choosing the appropriate alkene stereoisomer of the hydrazone. The E-alkenes led to the 1,4-syn isomers, while the Z-alkenes led to the 1,4-anti isomers, both with ≥20:1 diastereoselectivity.
- Qi, Wei,McIntosh, Matthias C.
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p. 357 - 359
(2008/09/19)
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- A unified synthetic approach to polyketides having both skeletal and stereochemical diversity
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An efficient systematic approach to the diversity-oriented synthesis of polyketides has been developed to provide both skeletal and stereochemical diversity. Each synthetic intermediate is also a desired polyketide fragment and no protecting group manipul
- Shang, Shiying,Iwadare, Hayato,Macks, Daniel E.,Ambrosini, Lisa M.,Tan, Derek S.
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p. 1895 - 1898
(2008/02/12)
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- Stereoselective total synthesis of zaragozic acid A based on an acetal [1,2] Wittig rearrangement
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A simultaneous creation of the C4 and C5 quaternary carbon centers by an acetal [1,2] Wittig rearrangement of O-glycoside 1 derived from L-arabino-γ-lactone is the key feature in the construction of the 2,8-dioxabicyclo[3.2.1]octane core structure of zara
- Tomooka, Katsuhiko,Kikuchi, Makoto,Igawa, Kazunobu,Suzuki, Masaki,Keong, Ping-Huai,Nakai, Takeshi
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p. 4502 - 4505
(2007/10/03)
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- Studies in polypropionate synthesis: High π-face selectivity in Syn and Anti aldol reactions of chiral boron enolates of lactate-derived ketones
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Use of (c)Hex2Bcl/Me2NEt in the aldol reactions of the α'-benzoyloxy ketone 7 with aldehydes leads to high stereoselectivity (97-95.5% ds) for the crystalline anti adducts 11. Under similar conditions, the corresponding benzyl ether 6 favours formation of the syn adducts 9.
- Paterson, Ian,Wallace, Debra J.,Velazquez, Silvia M.
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p. 9083 - 9086
(2007/10/02)
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