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Glycosyl Imidates, 42 Selectively Protected Lactose and 2-Azido Lactose, Building Blocks for Glycolipid Synthesis (1989)

Jung, Karl-Heinz ; Hoch, Monika ; Schmidt, Richard R.

Weinheim : Wiley-Blackwell

Liebigs Annalen 1989 (1989), S. 1099-1106

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ISSN: 0170-2041

Keywords: Lactose ; Azidolactose ; Glycosyl acceptors ; Glycosyl donors ; Regioselective protection ; Carbohydrates ; Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Description / Table of Contents: Glycosylimidate, 42. - Selektiv geschützte Lactose und 2-Azidolactose als Bausteine für die Synthese von GlycolipidenDurch regioselektive Alkylierung der 3′-OH-Gruppe von Benzyl-β-lactosid mit der Stannylierungsmethode wurden die 3′-OH- und 4′-OH-ungeschützten Lactosederivate 5 und 10 sowie das 4′-OH-ungeschützte Lactosederivat 9 hergestellt, das aufgrund seiner unterschiedlichen Schutzgruppe für 3′-OH für weitere Umwandlungen geeignet ist. Diese Bausteine sind wertvolle Glycosylakzeptoren für die Synthese von Glycolipiden. Zur Synthese von Glycosyldonoren mit Gal(β1 → 4)GlcNAc-Struktur wurde das 2-Azidolactosederivat 19 verwendet. Durch regioselektive Alkylierung der 3′-OH-Gruppe mit der Stannylierungsmethode sowie durch Anwendung anderer regioselektiver Schutzgruppen-Verfahren wurden die Trichloroacetimidate 17, 24 und 30 hergestellt, die aufgrund ihrer speziellen Schutzgruppen für 3′-OH, 4′-OH und 6′-OH für weitere Umwandlungen geeignet sind.

Notes: Performing regioselective alkylation at 3′-OH of benzyl β-lactoside 1 by the stannylation method we prepared the 3′-OH- and 4′-OH-unprotected lactose derivatives 5 and 10 and the 4′-OH-unprotected lactose derivative 9 containing a different protecting group at 3′-OH, suitable for further transformations. These building blocks are valuable glycosyl acceptors in glycolipid synthesis. For the synthesis of glycosyl donors with Gal(β1 → 4)GlcNAc-structure we used the 2-azido lactose derivative 19. By regioselective alkylation of 3′-OH by the stannylation method and application of other common regioselective protecting procedures we prepared the trichloroacetimidates 17, 24, and 30 containing special protecting groups at 3′-OH, 4′-OH, and 6′-OH which are suitable for further transformations in these positions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jlac.198919890276

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Functionally substituted vinyl carbanions, 43. Convenient transformation of hexopyranosides into α-methylene δ-lactone derivatives (1991)

Kast, Jürgen ; Hoch, Monika ; Schmidt, Richard R.

Weinheim : Wiley-Blackwell

Liebigs Annalen 1991 (1991), S. 481-485

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ISSN: 0170-2041

Keywords: Glycals, C-2 lithiation of ; α-Alkoxyvinyl phenyl sulfoxides, β-C lithiation of ; β-Alkoxy acrylates, β-C lithiation of ; β-Hydroxymethylvinyl phenyl sulfoxides, transformation into α-methylene carbonyl derivatives ; Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Treatment of glycopyranosyl phenyl sulfoxides 2ah, 1, 2bh, 1 with two equivalents of lithium diisopropylamide provides directly the C-2-lithiated glycal intermediates 3aAh, 1, 3bAh, 1 which, on reaction with formaldehyde as electrophile, furnish the 2-hydroxymethyl derivatives 4ah, 1 and 4bh, 1, respectively. These compounds are transformed at elevated temperature and by acid catalysis directly into the α-methylene-δ-lactones 5a, b. Correspondingly, from 2ah, 1 and methyl chloroformate as electrophile the 2-methoxycarbonyl derivatives 6h and 61, respectively, are obtained. Treatment of 6h, 1 with Raney nickel leads to 2-methoxycarbonyl-substituted glycal 7 containing a β-alkoxyacrylate moiety which again can be directly β-C-lithiated as demonstrated by the introduction of deuterium at C-1.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jlac.199119910187

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Oxokohlenstoffe und verwandte Verbindungen, VIII. Quadratsäureamidchloride: Einfache Zugangswege sowie Cyclisierung spezieller Vertreter zu anellierten Cyclobutendionen (1985)

Schmidt, Arthur H. ; Plaul, Wolfgang ; Aimène, Amokrane ; [et al.]

Weinheim : Wiley-Blackwell

Liebigs Annalen 1985 (1985), S. 1021-1035

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ISSN: 0170-2041

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Description / Table of Contents: Oxocarbons and Related Compounds, VIII1). - Squaric Amide Chlorides: Simple Methods of their Preparation and Cyclization of Specially Substituted Representatives to Annulated CyclobutenedionesSquaric dichloride (1c) reacts with a great number of secondary amines and with several primary amines to afford the squaric amide chlorides 4d - z. A further simple method for the preparation of 4a - d, aa - ac has been found in the reaction of 1c with an equimolar amount of the trimethylsilylamines 9a - ac. On using a twofold molar amount of 4-(trimethylsilyl)morpholine (9d), dimorpholinocyclobutenedione (11) has been obtained. Reaction of hexamethyldisilazane (12) with 1c affords 3-amino-4-chloro-3-cyclobutene-1,2-dione (14). The squaric amide chlorides 4m, u - w suffer intramolecular cyclization by the action of AlCl3 to give the annulated cyclobutenediones 17a - d. The analogous cyclization of 4z yields 18 which is characterized by a sevenmembered ring condensed with the cyclobutenedione unit.

Notes: Quadratsäuredichlorid (1c) reagiert mit einer Vielzahl von sekundären und einigen primären Aminen zu den Quadratsäureamidchloriden 4d - z. Zur Erzielung optimaler Produktausbeuten werden die Reaktionsbedingungen systematisch untersucht. Auf einfachem Weg werden 4a - d, aa - ac auch durch Umsetzung von 1c mit der äquimolaren Menge der Trimethylsilylamine 9a - ac erhalten. Der Einsatz einer doppeltmolaren Menge 4-(Trimethylsilyl)morpholin (9d) führt zu Dimorpholinocyclobutendion (11). Die Einwirkung von Hexamethyldisilazan (12) auf 1c liefert 3-Amino-4-chlor-3-cyclobuten-1,2-dion (14). Die Quadratsäureamidchloride 4m, u - w erfahren unter dem Einfluß von AlCl3 intramolekulare Cyclisierung zu den anellierten Cyclobutendionen 17a - d. Bei der gleichartigen Cyclisierung von 4z entsteht in guter Ausbeute 18, in dem das Cyclobutendionsystem an ein siebengliedriges Ringsystem kondensiert ist.

Additional Material: 4 Tab.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jlac.198519850516

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De-novo-Synthese von Kohlenhydraten und verwandten Naturstoffen, 32 Die inverse Hetero-Diels-Alder-Reaktion zur Synthese von Teilsequenzen für Polyketid-Naturstoffe (1988)

Schmidt, Richard R. ; Haag-Zeino, Brigitte ; Hoch, Monika

Weinheim : Wiley-Blackwell

Liebigs Annalen 1988 (1988), S. 885-889

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ISSN: 0170-2041

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Description / Table of Contents: De novo Synthesis of Carbohydrates and Related Natural Products, 321). - The Inverse Type Hetero-Diels-Alder Reaction for the Synthesis of Partial Structures of Polyketide Natural ProductsInverse type hetero-Diels-Alder reaction of the 1-oxa-1,3-diene 1a as heterodiene with (Z) ethyl 1-propenyl ether as dienophile afforded in an endo-specific cycloaddition reaction the persubstituted 3,4-dihydro-2H-pyran 2a. Convenient regio- and diastereospecific transformations furnished the 2-deoxy-2-methyl-manno-hexopyranoside 8; oxidation of this compound and subsequent Wittig reaction, hydrogenation, and acetylation gave diastereoselectively the 2,4-dideoxy-2,4-dimethyl-talo-hexopyranoside 12.

Notes: Die inverse Hetero-Diels-Alder-Reaktion des 1-Oxa-1,3-diens 1a als Heterodien mit (Z)-Ethyl-1-propenylether als Dienophil lieferte in einer endo-spezifischen Cycloaddition das persubstituierte 3,4-Dihydro-2H-pyran 2a. Durch einfache regio- und diastereo-spezifische Umwandlungen wurde das 2-Desoxy-2-methyl-manno-hexopyranosid 8 erhalten, das durch Oxidation, Wittig-Reaktion, Hydrierung und Acetylierung diastereoselektiv zum 2,4-Didesoxy-2,4-dimethyl-talo-hexopyranosid 12 führte.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jlac.198819880912

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