Showing papers by "Seiichiro Ogawa published in 1989"
TL;DR: In this paper, a tetrahydrofuropyran-5-one possessing significant cytotoxicity against several tumor cell lines, has been achieved by using L-arabinose as the redundant starting material.
Abstract: Enantiospecific total synthesis of (+)-altholactone [(+)-goniothalenol] (1), a novel tetrahydrofuropyran-5-one possessing significant cytotoxicity against several tumor cell lines, has been achieved by using L-arabinose as the redundant starting material The pivotal tetrahydrofuran formation was realized by treatment of the diastereomeric mixture of (2S,3R)-4,5-epoxy-5-phenyl-1,2,3-pentanetriol 1,3-benzylidene acetals 8 and 8′ with silica gel Simultaneous stereochemical inversion at C-4 and C-5 of the major cyclization product, O,O′-benzylidene derivative of (2S,3R,4S,5S)-2-(hydroxymethyl)-5-phenyltetrahydrofuran-3,4-diol (11), to the 2S,3R,4R,5R diastereomer 10 was achieved by hydroboration of (2S,3S)-3-hydroxy-2-(hydroxymethyl)-5-phenyl-2,3-dihydrofuran O,O′-benzylidene derivative (18) which derived from 11 Pfitzner-Moffatt oxidation of 10 followed by NaBH4 reduction gave the 2S,3R,4S,5R diastereomer 20 exclusively Displacement of the triflate group in (2S,3R,4S,5S)-2-(hydroxymethyl)-5-phenyl-4-[(tr
33 citations
TL;DR: In this paper, Quebrachitol was converted into -and -galactose derivatives via the common intermediate, the 7-membered hemiacetal-lactone, which was obtained by regioselective Baeyer-Villiger oxidation of the inosose.
26 citations
TL;DR: The first total synthesis of acarbose was described in this article, where the α- d -glucosidase inhibitor acarbose (1a) was described.
24 citations
22 citations
TL;DR: The first complete synthesis of antibiotic hygromycin A was reported in this paper, where the protected sugar moiety and the aminocyclitol derived from D-glucose as the optically active from, followed by deprotection, gives the product (1) which was identified with an aunthentic sample by 400 MHz 1H n.m.r. spectroscopy.
Abstract: The first complete synthesis of antibiotic hygromycin A is reported; coupling of the protected sugar moiety (2) and the aminocyclitol (3) derived from D-glucose as the optically active from, followed by deprotection, gives the product (1) which was identified with an aunthentic sample by 400 MHz 1H n.m.r. spectroscopy.
17 citations
TL;DR: A new synthesis of nojirimycin from seven-membered hemiacetal lactones derived from myo-inositol by a five-step reaction was reported in this article.
Abstract: A report of a new synthesis of nojirimycin (1a), as well as its antipode (1b), from optically active seven-membered hemiacetal lactones (2a,b) derived from myo-inositol by a five step reaction; the hydrogen sulphite adduct of (1b) shows high inhibitory activity against β-glucosidase and α-mannosidase, being almost comparable to that of mannojirimycin.
15 citations
TL;DR: The (E)- and (Z)-isomers (2E and 2Z) of 3-O-benzyl-5,6-dideoxy-1,2-Oisopropylidene-α -D-xylo-hept-5-eno-1-4-furanose were subjected to Claisen rearrangement with triethyl orthoacetate as discussed by the authors.
Abstract: The (E)- and (Z)-isomers (2E and 2Z) of 3-O-benzyl-5,6-dideoxy-1,2-O-isopropylidene-α -D-xylo-hept-5-eno-1,4-furanose were subjected to Claisen rearrangement with triethyl orthoacetate. Possible two diastereomers were obtained as a 1 to 1 mixture from both of 2Z and 2E, and also from their 3-hydroxy or 3-siloxy derivatives. On the other hand, the rearrangement of the corresponding D-ribo derivative (13Z) and its 3-O-(t-butyldiphenylsilyl) derivative proceeded with a high level of diastereoselectivity. By contrast, the (E)-isomer of 13Z showed no significant stereoselectivity, resulting in the formation of a diastereomeric mixture. The configurations of the introduced stereogenic centers by the rearrangements were unambiguously established by chemical transformations.
14 citations
14 citations
TL;DR: In this article, the reaction of validoxylamine A derivatives with N-bromosuccinimide in aqueous N,N-dimethylformamide resulted in a cleavage of the imino bonds to give rise to synthetically useful protected derivatives of (+)-validamine and valienamine, and the cyclohexanone and -hexenone derivatives.
Abstract: Reaction of validoxylamine A derivatives with N-bromosuccinimide in aqueous N,N-dimethylformamide resulted in a cleavage of the imino bonds to give rise to synthetically useful protected derivatives of (+)-validamine and valienamine, and the cyclohexanone and -hexenone derivatives.
13 citations
TL;DR: In this paper, a promising antiviral carbocyclic nucleoside analogue was synthesized enantiospecifically using a coupling reaction of 5amino-4,6-dichloropyrimidine and (1R,2R,3R,4R)-2,3-dihydroxy-4-(hydroxymethyl)cyclopentanamine which was in turn prepared from D-xylose.
Abstract: The title compound, a promising antiviral carbocyclic nucleoside analogue, was synthesized enantiospecifically. The present synthesis involves a coupling reaction of 5-amino-4,6-dichloropyrimidine and (1R,2R,3R,4R)-2,3-dihydroxy-4-(hydroxymethyl)cyclopentanamine which was in turn prepared from D-xylose.
12 citations
TL;DR: The validoxylamine A derivative obtained was convertible, by glycosylation followed by deprotection, into validamycins A, E, and their analogues, which constitutes a total synthesis thereof.
Abstract: (+)-Validoxylamine A (1) has been completely synthesized by deoxygenation of the validoxylamine B derivative (6) through formation of the aziridine, nucleophilic displacement with toluenethiol, reduction with Raney nickel, and deprotection. The validoxylamine A derivative (10) obtained was convertible, by glycosylation followed by deprotection, into validamycins A (2), E (3), and their analogues, which constitutes a total synthesis thereof.
TL;DR: Synthese de pseudo amino-4 desoxy-4 et pseudo amino 4 didesoxy- 4,7 glucopyranose a partir de dimethyl-2,2 tribenzyloxy-6,7,8 benzodioxanne-1,3
TL;DR: In this paper, the dialdehyde generated by periodate oxidation of (±)-2 exo,3 exo -dihydroxy-5 endo -hydroxymethyl-7-oxabicyclo[2.2.1]-heptane (2) in methanolic sodium methoxide afforded, after neutralisation, three diastereoisomers ( 4a-6a ) of (´)-2,4-dihdiox-6-hydroxmethyl-3-nitro-8-oxabelo[3
TL;DR: In this article, a promising antiviral carbocyclic nucleoside analogue was synthesized enantiospecifically using a coupling reaction of 5amino-4,6-dichloropyrimidine and (1R,2R,3R,4R)-2,3-dihydroxy-4-(hydroxymethyl)cyclopentanamine which was in turn prepared from D-xylose.
Abstract: The title compound, a promising antiviral carbocyclic nucleoside analogue, was synthesized enantiospecifically. The present synthesis involves a coupling reaction of 5-amino-4,6-dichloropyrimidine and (1R,2R,3R,4R)-2,3-dihydroxy-4-(hydroxymethyl)cyclopentanamine which was in turn prepared from D-xylose.
TL;DR: The first complete synthesis of validamycin B and validoxylamine B was reported in this paper, where the epoxide was coupled with the partially protected derivative (16) of (+)-valienamine, followed by deprotection, which was identified from the 1H n.m.r. spectrum of its totally O-acetylated derivative (1b).
Abstract: The first complete synthesis of validamycin B (1a) and validoxylamine B (2a) is reported; coupling of the epoxide (12) and the partially protected derivative (16) of (+)-valienamine, followed by deprotection, gives (1a), which was identified from the 1H n.m.r. spectrum of its totally O-acetylated derivative (1b). Alternatively, coupling of the epoxide (24) with the amine (16) affords compound (25), the structure of which can be established by converting (25) into validoxylamine B nona-O-acetate (2b). The appropriately protected amine (29) derived from (25) is glycosylated, followed by deprotection and acetylation, to give (1b).
TL;DR: In this paper, a tetrahydrofuropyran-5-one possessing significant cytotoxicity against several tumor cell lines, has been achieved by using L-arabinose as the redundant starting material.
Abstract: Enantiospecific total synthesis of (+)-altholactone [(+)-goniothalenol] (1), a novel tetrahydrofuropyran-5-one possessing significant cytotoxicity against several tumor cell lines, has been achieved by using L-arabinose as the redundant starting material. The pivotal tetrahydrofuran formation was realized by treatment of the diastereomeric mixture of (2S,3R)-4,5-epoxy-5-phenyl-1,2,3-pentanetriol 1,3-benzylidene acetals 8 and 8′ with silica gel. Simultaneous stereochemical inversion at C-4 and C-5 of the major cyclization product, O,O′-benzylidene derivative of (2S,3R,4S,5S)-2-(hydroxymethyl)-5-phenyltetrahydrofuran-3,4-diol (11), to the 2S,3R,4R,5R diastereomer 10 was achieved by hydroboration of (2S,3S)-3-hydroxy-2-(hydroxymethyl)-5-phenyl-2,3-dihydrofuran O,O′-benzylidene derivative (18) which derived from 11. Pfitzner-Moffatt oxidation of 10 followed by NaBH4 reduction gave the 2S,3R,4S,5R diastereomer 20 exclusively. Displacement of the triflate group in (2S,3R,4S,5S)-2-(hydroxymethyl)-5-phenyl-4-[(tr...