Search results for "Chlorosulfonyl isocyanate"
showing 4 items of 4 documents
Synthese von 2-Acyloxy- und 2-Alkyloxy-3-ketoglycalen und ihren Bromaddukten
1983
Die an den Hydroxygruppen acetyl-, pivaloyl- und methylgeschutzten 2-Hydroxy-3-ketoglycale 5a, 5b bzw. 11 werden durch Oxidation der entsprechenden 1-O-Acylglucopyranosen 3a, 3b bzw. 9 an der freien 3-Hydroxygruppe mit Dimethylsulfoxid/Acetanhydrid oder Chlorsulfonylisocyanat hergestellt und charakterisiert. Nur beim Acetylderivat 3a verlaufen die Oxidation und die Eliminierung des 1-Acetyloxysubstituenten in einem Schritt. Beim Pivaloylderivat 3b und beim Methylderivat 9 mus die Eliminierung aus der 3-Ulose 4 bzw. 10 mit Diazabicycloundecen (DBU) vervollstandigt werden. – Die geschutzten Hex-1-enopyran-3-ulosen 5a, 5b und 11 addieren Brom stereoselektiv unter Bildung der D-ribo-konfigurier…
Diversity-Oriented Synthesis of Highly Functionalized Alicycles across Dipolar Cycloaddition/Metathesis Reaction
2021
AbstractThis Account gives an insight into the selective functionalization of some readily available commercial cyclodienes across simple chemical transformations into functionalized small-molecular scaffolds. The syntheses involved selective cycloadditions, followed by ring-opening metathesis (ROM) of the resulting azetidin-2-one derivatives or isoxazoline frameworks and selective cross metathesis (CM) by discrimination of the C=C bonds on the alkenylated heterocycles. The CM protocols have been described when investigated under various conditions with the purpose on exploring chemodifferentiation of the olefin bonds and a study on the access of the corresponding functionalized β-lactam or…
Regio- and stereoselective synthesis of the enantiomers of monoterpene-based β-amino acid derivatives
2007
Abstract The regio- and stereospecific addition of chlorosulfonyl isocyanate to cis-δ-pinene enantiomers has furnished monoterpene-fused β-lactams. The observed regioselectivity can be explained by ab initio DFT modeling of transition state structures. In contrast with the less reactive α-pinane-fused β-lactam 4, the resulting β-lactams 5 and 13 containing an amino group connected to a secondary carbon possess similar reactivity to the cycloalkane-fused analogues and can be easily converted to the β-amino acid and its protected derivatives. The base-catalyzed isomerization of the cis-amino ester afforded the corresponding trans-amino ester in moderate yield.
Regio- and stereoselective synthesis of constrained enantiomeric β-amino acid derivatives
2008
Abstract Chlorosulfonyl isocyanate addition to (−)- and (+)-apopinene furnished monoterpene-fused β-lactams in highly regio- and stereospecific reactions. β-Lactams 5 and 13 exhibited reactivities similar to those of the cycloalkane-fused analogs and were easily converted to the β-amino acid and its protected derivatives. The base-catalyzed isomerization of the cis -amino ester afforded the corresponding trans -amino acid enantiomers in excellent yields. The complete isomerization is explained by the stability difference, which was estimated by ab initio calculations between the cis- and trans -diastereomers.