Showing papers by "Seiichiro Ogawa published in 1993"
TL;DR: A preliminary biological assay revealed that the stereochemistry at the 2-position of lycoricidine plays an important role in its cytotoxic activity.
Abstract: Stereoselective total synthesis of antimitotic alkaloid (+)-lycoricidine (1) and its 2-epimer (30) was accomplished starting from D-glucose. The key steps in this synthesis are (i) a catalytic version of the Ferrier rearrangement for the preparation of the optically active substituted cyclohexenone (the C-ring of lycoricidine) and (ii) a Pd-catalyzed intramolecular Heck-type reaction for construction of the phenanthridone skeleton. A preliminary biological assay revealed that the stereochemistry at the 2-position of lycoricidine plays an important role in its cytotoxic activity
75 citations
26 citations
26 citations
TL;DR: In this paper, D-Glucose-derived α,β-unsaturated ester 17, which includes a geminally and differentially substituted γ-carbon and a terminal aldehyde functionality, was subjected to a SmI 2 -mediated intramolecular reductive coupling reaction in a THF solution containing 1/10 volume of HMPA.
Abstract: D-Glucose-derived α,β-unsaturated ester 17, which includes a geminally and differentially substituted γ-carbon and a terminal aldehyde functionality, was subjected to a SmI 2 -mediated intramolecular reductive coupling reaction in a THF solution containing 1/10 volume of HMPA. The reaction proceeded with moderate stereoselectivity to provide a diastereomeric mixture of hexahydrobenzofuran-2(3H)-ones, in which cis-fused product 25 was obtained as the major isomer in 35% isolated yield. Two trans-fused coupling products 26 (17%) and 27 (14%) were also obtained. Starting from major product 25, the insect sex attractant (-)-anastrephin (1) and (-)-epianastrephin (2) were synthesized enantiospecifically. Two unnatural stereocongeners, (-)-7a-epi-anastrephin (3) and (-)-7a-epi-epianastrephin (4), were also derived from 25
23 citations
TL;DR: The total synthesis of trehalase inhibitor, trehazolin has been accomplished by coupling the optically active aminocyclopentanepentaol with α-D-glucopyranosylisothiocyanate derivative, followed by subsequent oxazoline-ring formation and removal of the protecting groups, thereby confirming its absolute configuration as mentioned in this paper.
Abstract: The total synthesis of trehalase inhibitor, trehazolin has been accomplished by coupling the optically active aminocyclopentanepentaol with α-D-glucopyranosylisothiocyanate derivative, followed by subsequent oxazoline-ring formation and removal of the protecting groups, thereby confirming its absolute configuration.
20 citations
13 citations
TL;DR: Some oxo-linked 5a-carba-di and tri-saccharides of biological interests including 5a carbamaltose, were synthesized by coupling of 5a carba-glycosyl donor, 1,2-anhydro-5a-Carba-β-D-mannopyranose derivative with the alkoxides generated from the protected hexopyransose derivatives in N,N-dimethylformamide in the presence of a crown ether.
Abstract: Some oxo-linked 5a-carba-di- and tri-saccharides of biological interests including 5a-carbamaltose, were synthesized by coupling of 5a-carba-glycosyl donor, 1,2-anhydro-5a-carba-β-D-mannopyranose derivative with the alkoxides generated from the protected hexopyranose derivatives in N,N-dimethylformamide in the presence of a crown ether.
13 citations
TL;DR: In this article, the stereoselective conversion of the naturally occurring optically active cyclitol, L-quebrachitol 2, into antifungal β-methoxyacrylate, oudemansin X 1 is described.
Abstract: The stereoselective conversion of the naturally occurring optically active cyclitol, L-quebrachitol 2, into antifungal β-methoxyacrylate, oudemansin X 1 is described. This first total synthesis of 1 fully confirmed the proposed absolute configuration of the antibiotic and showed the importance of 2 as a versatile chiral starting material in natural product syntheses.
12 citations
TL;DR: Dicarba-α,α-trehalose 2a, bis-(5a-carba- α-D-glucopyranosyl)amine, was prepared by the coupling of di-O-isopropylidene-α-validamine 5 and protected carba-sugar epoxide 7, followed by removal of the 2′-hydroxy group and conventional deprotection as discussed by the authors.
Abstract: Dicarba-α,α-trehalose 2a, bis-(5a-carba-α-D-glucopyranosyl)amine, was prepared by the coupling of di-O-isopropylidene-α-validamine 5 and protected carba-sugar epoxide 7, followed by removal of the 2′-hydroxy group and conventional deprotection. Likewise, imino-linked dicarba-α,α-trehalose analogues 3a and 4a, composed of valienamine and valiolamine moieties, were synthesized by reaction of protected valienamine 6 and valiolamine 24 with the epoxides 7 and 29, respectively. Compounds 2a, 3a, and 4a were shown to possess strong inhibitory activity against trehalase, being compatible with validoxylamine A 1.
12 citations
TL;DR: Complete synthesis of both diastereoisomeric structures, initially proposed for the trehalase inhibitor trehalostatin, and their biological assay have been carried out, suggesting that the inhibitor would possess convincingly its 4′-epimeric structure later assigned for trehazolin.
Abstract: Complete synthesis of both diastereoisomeric structures, initially proposed for the trehalase inhibitor trehalostatin, and their biological assay have been carried out. The synthetic compounds were found to lack an inhibitory activity against trehalase, suggesting that the inhibitor would possess convincingly its 4′-epimeric structure later assigned for trehazolin.
9 citations
TL;DR: Intramolecular Diels-Alder cycloaddition of enantiomerically enriched triene 16 could be attained under thermal conditions resulting in the formation of octahydronaphthalene derivatives 17–20, one of which was converted into PI-201 (1), a new platelet aggregation inhibitor.
TL;DR: In this paper, an Intramolecular radical cyclization of D-glucose-derived substrate, (2R,3R,4R,5S)-2, 3-(isopropylidenedioxy)-5-[(1R)-l, 2-(iso-propylidensioxy)ethyl]-4-[3-bromo-3, 3-bis(methoxycarbonyl)propyl]-4-vinyltetrahydrofuran, 7 proceeded in a 6-endo-trig
TL;DR: In this paper, the Claisen rearrangement of branched-chain furanose 5, which has an allylic alcohol function as a side chain, by heating in triethyl orthoacetate afforded a diastereomeric mixture 6 of the rearrangements products and the ratio of the products was estimated to be nearly 3:1 based on 1H NMR analysis.
TL;DR: In this paper, the authors showed that the introduction of the acetamido or amino function instead of the hydroxyl group into the C-6′ position of the methyl acarviosin analog resulted in an appreciable decrease of the inhibitory activity.
TL;DR: Dicarba-α,α-trehalose 2a, bis-(5a-carba- α-D-glucopyranosyl)amine, was prepared by the coupling of di-O-isopropylidene-α-validamine 5 and protected carba-sugar epoxide 7, followed by removal of the 2′-hydroxy group and conventional deprotection.
Abstract: Dicarba-α,α-trehalose 2a, bis-(5a-carba-α-D-glucopyranosyl)amine, was prepared by the coupling of di-O-isopropylidene-α-validamine 5 and protected carba-sugar epoxide 7, followed by removal of the 2′-hydroxy group and conventional deprotection. Likewise, imino-linked dicarba-α,α-trehalose analogues 3a and 4a, composed of valienamine and valiolamine moieties, were synthesized by reaction of protected valienamine 6 and valiolamine 24 with the epoxides 7 and 29, respectively. Compounds 2a, 3a, and 4a were shown to possess strong inhibitory activity against trehalase, being compatible with validoxylamine A 1.
TL;DR: In this article, a reductive cyclization of enantiomerically pure γ,γ-differentially C-substituted α,β-unsaturated ester with terminal aldehyde functionality was achieved using SmI 2 in THF-HMPA.
Abstract: Intramolecular reductive cyclization of enantiomerically pure γ,γ-differentially C-substituted α,β-unsaturated ester 5 having a terminal aldehyde functionality, was effectively achieved using SmI 2 in THF-HMPA. Starting with the major cyclization product 6 , enantiospecific total synthesis of (−)-anastrephin. 1 was completed.