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Akira Sasaki

Other affiliations: Sumitomo Chemical
Bio: Akira Sasaki is an academic researcher from Kwansei Gakuin University. The author has contributed to research in topics: Protecting group & Dieckmann condensation. The author has an hindex of 2, co-authored 5 publications receiving 27 citations. Previous affiliations of Akira Sasaki include Sumitomo Chemical.

Papers
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Journal ArticleDOI
TL;DR: An efficient, practical, and stereocontrolled synthesis of 1β-methyl carbapenems has been performed utilizing a new dehydration type of Ti-Dieckmann (intramolecular Ti-Claisen) condensation.
Abstract: An efficient, practical, and stereocontrolled synthesis of 1β-methylcarbapenems has been performed utilizing a new dehydration type of Ti-Dieckmann (intramolecular Ti-Claisen) condensation. This cyclization reaction has the advantage of direct incorporation of the thiol moiety into the target 1β-methylcarbapenem, compared with the traditional basic Dieckmann condensation. Another advantage is the use of environmentally benign (low toxicity and safe) reagents (TiCl4 and Et3N or Bu3N).

22 citations

Patent
13 Oct 1983
TL;DR: In this paper, a Schiff base with diketene in the presence of an imidazole was used to produce β-Lactam compounds which are useful as intermediates for the production of carbapenem or penem derivatives and a process for producing the same.
Abstract: β-Lactam compounds which are useful as intermediates for the production of carbapenem or penem derivatives and a process for producing the same. The process comprises reacting a Schiff base with diketene in the presence of an imidazole, reducing the acetyl group of the resulting N-protected-3-acetyl-2-azetidinone-4-carboxylic acid ester, and removing the protecting group for a carboxyl group from the resulting 3-(1-hydroxyethyl)-2-azetidinone-4-carboxylic acid derivative.

5 citations

Patent
17 Jan 1991
TL;DR: An amino acid compound of the formula: --CH.sub.2 SR.5 (wherein R5 is an aryl group or an ar(lower)alkyl group), which is a useful intermediate in the synthesis of 1-alkyl carbapenem compounds.
Abstract: An amino acid compound of the formula: ##STR1## wherein R is a lower alkyl group, R1 is a hydrogen atom or a protecting group for carboxyl, R2 is a hydrogen atom, a protecting group for amino, an optionally substituted allyl group of the formula: ##STR2## (wherein R3 and R4 are each a hydrogen atom, a lower alkyl group or an aryl group), a beta-hydroxyethyl group in which the hydroxyl group is optionally protected, a formylmethyl group in which the formyl group is optionally protected, a carboxymethyl group in which the carboxyl group is protected or a 2-furylmethyl group and X is an optionally protected carboxyl group, a hydroxymethyl group in which the hydroxyl group is optionally protected or a substituted mercaptomethyl group of the formula: --CH.sub.2 SR.sub.5 (wherein R5 is an aryl group or an ar(lower)alkyl group), which is a useful intermediate in the synthesis of 1-alkylcarbapenem compounds.
Journal ArticleDOI
TL;DR: An efficient, practical, and stereocontrolled synthesis of 1β-methyl carbapenems has been performed utilizing a new dehydration type of Ti-Dieckmann (intramolecular Ti-Claisen) condensation.
Abstract: An efficient, practical, and stereocontrolled synthesis of 1β-methylcarbapenems has been performed utilizing a new dehydration type of Ti-Dieckmann (intramolecular Ti-Claisen) condensation. This cyclization reaction has the advantage of direct incorporation of the thiol moiety into the target 1β-methylcarbapenem, compared with the traditional basic Dieckmann condensation. Another advantage is the use of environmentally benign (low toxicity and safe) reagents (TiCl4 and Et3N or Bu3N).

Cited by
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Journal ArticleDOI
TL;DR: Ti-crossed-Claisen condensation between a 1:1 mixture of carboxylic esters and acid chlorides promoted by TiCl4-Bu3N-N-methylimidazole proceeded successfully to give various beta-keto esters in good yields with excellent selectivities.
Abstract: Ti-crossed-Claisen condensation between a 1:1 mixture of carboxylic esters and acid chlorides promoted by TiCl4−Bu3N-N-methylimidazole proceeded successfully to give various β-keto esters in good yields with excellent selectivities (19 examples, ∼48−95% yield; cross/self-selectivity = ∼96/4−99/1). The present method was extended to the condensation between a 1:1 mixture of carboxylic acids and carboxylic esters (six examples, ∼70−92% yield; cross/self-selectivity = ∼91/9−99/1). To demonstrate the utility of the present two Ti-crossed-Claisen condensations, we performed a couple of efficient short-step syntheses of two natural, representative, and useful perfumes, cis-jasmone and (R)-muscone.

84 citations

Journal ArticleDOI
Akira Iida1, Jun Osada1, Ryohei Nagase1, Tomonori Misaki1, Yoo Tanabe1 
TL;DR: A pentafluorophenylammonium triflate (PFPAT) catalyst successfully promoted C-acylation of enol silyl ethers with acid chloride to produce various beta-diketones and proceeded smoothly to provide alpha-monoalkylated beta-keto (thio)esters in good to excellent yield.

45 citations

Journal ArticleDOI
TL;DR: A powerful Ti-crossed Claisen condensation between ketene silyl acetals and acid chlorides was successfully performed to give alpha-monoalkylated esters and thermodynamically unfavorable alpha,alpha-dialkylated beta-keto esters in good yield.

37 citations

Journal ArticleDOI
TL;DR: The presented mechanistic hypothesis allows one to better understand the pivotal role of titanium(IV) in the reaction, and points to a three-step mechanism: Ti-induced formation of the enolate ion, aldol reaction between theEnolate ion and the aldehyde, both coordinated to titanium.
Abstract: The condensation of dialkyl b-diesters with various aldehydes pro- moted by TiCl4 has been studied by DFT approaches and experimental methods, including NMR, IR and UV/ Vis spectroscopy. Various possible reac- tion pathways have been investigated and their energy profiles evaluated to find out a plausible mechanism of the reaction. Theoretical results and exper- imental evidence point to a three-step mechanism: 1) Ti-induced formation of the enolate ion; 2) aldol reaction be- tween the enolate ion and the alde- hyde, both coordinated to titanium; and 3) intramolecular elimination that leads to a titanyl complex. The present- ed mechanistic hypothesis allows one to better understand the pivotal role of titanium(IV) in the reaction.

33 citations

Journal ArticleDOI
TL;DR: Using the present reaction as the key step, an efficient short synthesis of three lactone [2(5H)-furanone] analogs of jasmine perfumes was performed, and the lactone analog of cis-jasmone had a unique perfume property (tabac).
Abstract: An efficient TiCl(4)-Et(3)N or Bu(3)N-promoted aldol-type addition of phenyl and thiophenyl esters or thioaryl esters with aldehydes and ketones was performed (total 46 examples). The present method is advantageous from atom-economical and cost-effective viewpoints; good to excellent yields, moderate to good syn-selectivity, substrate variations, reagent availability, and simple procedures. Utilizing the present reaction as the key step, an efficient short synthesis of three lactone [2(5H)-furanone] analogs of jasmine perfumes was performed. Among them, the lactone analog of cis-jasmone had a unique perfume property (tabac).

31 citations