Photochemistry of 2-azido-2-alkyl-3-oxobutanoic esters and amides

1990 ◽  
Vol 68 (8) ◽  
pp. 1425-1436 ◽  
Author(s):  
Oliver E. Edwards ◽  
Werner Rank
Keyword(s):  
Double Bond ◽  
Acyl Migration ◽  
Double Bond Migration ◽  
Keto Ester ◽  
Dehydroamino Acid ◽  
Acid Esters

Photolysis of 2-alkyl-2-azido-3-oxobutanoic esters and amides gave products resulting from alkyl or acyl migration onto nitrogen. The resulting ketimimes could be isolated in moderate purity, but the N-acyl imines were rapidly converted into solvation products or enamides (N-acetyl dehydroamino acid esters) resulting from double bond migration. Mechanisms for formation of these products are discussed. The N-(2-azido-2-methyl-3-oxobutanoyl) derivative of the diketopiperazine from L-valyl-L-proline gave a stereoisomer of the cyclol tripeptide unit of ergovaline. Keywords: N-acyl imines, mechanism of 2-azido-3-keto ester photolysis, cyclol tripeptide synthesis, ergovaline.

Remote double bond migration via rhodium catalysis: a novel enone transposition

1976 ◽  
Vol 98 (22) ◽  
pp. 7102-7104 ◽  
Author(s):  
Paul A. Grieco ◽  
Mugio Nishizawa ◽  
Nebojsa Marinovic ◽  
William J. Ehmann
Keyword(s):  
Double Bond ◽  
Rhodium Catalysis ◽  
Double Bond Migration

ChemInform Abstract: Double-Bond Migration in Pyrano(4,3-b)pyrylium Cations.

ChemInform ◽  
2010 ◽  
Vol 25 (8) ◽  
pp. no-no
Author(s):  
F. M. DEAN ◽  
M. MALKI ◽  
L. J. O'KEEFFE
Keyword(s):  
Double Bond ◽  
Double Bond Migration

scholarly journals Oxepinamide F biosynthesis involves enzymatic d-aminoacyl epimerization, 3H-oxepin formation, and hydroxylation induced double bond migration

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Liujuan Zheng ◽  
Haowen Wang ◽  
Aili Fan ◽  
Shu-Ming Li
Keyword(s):  
Cytochrome P450 ◽  
Double Bond ◽  
Biosynthetic Pathway ◽  
Hydroxyl Group ◽  
Cytochrome P450 Enzyme ◽  
Double Bond Migration ◽  
Feeding Experiments ◽  
Aspergillus Ustus ◽  
P450 Enzyme ◽  
Derivatives Of

Abstract Oxepinamides are derivatives of anthranilyl-containing tripeptides and share an oxepin ring and a fused pyrimidinone moiety. To the best of our knowledge, no studies have been reported on the elucidation of an oxepinamide biosynthetic pathway and conversion of a quinazolinone to a pyrimidinone-fused 1H-oxepin framework by a cytochrome P450 enzyme in fungal natural product biosynthesis. Here we report the isolation of oxepinamide F from Aspergillus ustus and identification of its biosynthetic pathway by gene deletion, heterologous expression, feeding experiments, and enzyme assays. The nonribosomal peptide synthase (NRPS) OpaA assembles the quinazolinone core with d-Phe incorporation. The cytochrome P450 enzyme OpaB catalyzes alone the oxepin ring formation. The flavoenzyme OpaC installs subsequently one hydroxyl group at the oxepin ring, accompanied by double bond migration. The epimerase OpaE changes the d-Phe residue back to l-form, which is essential for the final methylation by OpaF.

scholarly journals Colochiroside E, an Unusual Non-holostane Triterpene Sulfated Trioside from the Sea Cucumber Colochirus Robustus and Evidence of the Impossibility of a 7(8)-Double Bond Migration in Lanostane Derivatives having an 18(16)-Lactone

2016 ◽  
Vol 11 (6) ◽  
pp. 1934578X1601100 ◽  
Author(s):  
Alexandra S. Silchenko ◽  
Anatoly L Kalinovsky ◽  
Sergey A. Avilov ◽  
Pelageya V. Andryjaschenko ◽  
Pavel S. Dmitrenok ◽  
...  
Keyword(s):  
Double Bond ◽  
Triterpene Glycoside ◽  
Sea Cucumber ◽  
Carbohydrate Chain ◽  
2D Nmr ◽  
Double Bond Migration ◽  
Chlorine Derivative ◽  
Rare Group

The unusual non-holostane triterpene glycoside, colochiroside E (1) was isolated from the sea cucumber Colochirus robustus (Cucumariidae, Dendrochirotida). The structure of 1 was established by analysis of ID, 2D NMR and HRESI MS data. Colochiroside E (1) belongs to a rare group of glycosylated 9β-H-lanosta-18(16)-lactones and has an unprecedented sulfated trisaccharide carbohydrate chain consisting of two glucose and one xylose units. In contrast with (9β-H)-7(8)-unsaturated holostane glycosides, the 7(8)-double bond in the having (9β-H)-configuration aglycone of colochiroside E is not capable of migration into the 8(9)- and then into the 9(11)-position on treatment with HC1. The formation of a chlorine derivative of 1 was observed under these conditions.

scholarly journals Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides

2020 ◽  
Vol 16 ◽  
pp. 818-832 ◽  
Author(s):  
Péter Bagi ◽  
Réka Herbay ◽  
Nikolett Péczka ◽  
Zoltán Mucsi ◽  
István Timári ◽  
...  
Keyword(s):  
Double Bond ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Methanesulfonic Acid ◽  
Thermal Conditions ◽  
Double Bond Migration ◽  
Bond Rearrangement ◽  
Migration Pathways

A series of 1-substituted-3-methyl-2-phospholene oxides was prepared from the corresponding 3-phospholene oxides by double bond rearrangement. The 2-phospholene oxides could be obtained by heating the 3-phospholene oxides in methanesulfonic acid, or via the formation of cyclic chlorophosphonium salts. Whereas mixtures of the 2- and 3-phospholene oxides formed, when the isomerization of 3-phospholene oxides was attempted under thermal conditions, or in the presence of a base. The mechanisms of the various double bond migration pathways were elucidated by quantum chemical calculations.

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