Spontaneous butenolide ring formation of pregnane-21-O-malonyl hemiesters under mild reaction conditions is facilitated by the 14β-hydroxy group present in all natural cardenolides

Tetrahedron ◽  
2016 ◽  
Vol 72 (30) ◽  
pp. 4556-4563 ◽  
Author(s):  
R.M. Pádua ◽  
N. Meitinger ◽  
M. Hennemann ◽  
P. Schebitz ◽  
R. Waibel ◽  
...  
Keyword(s):  
Hydroxy Group ◽  
Ring Formation ◽  
Reaction Conditions

Transformation of 8-[(2-Hydroxyalkyl)sulfanyl]adenines to 6-Amino-7H-purin-8(9H)-one Derivatives

2001 ◽  
Vol 66 (9) ◽  
pp. 1393-1406 ◽  
Author(s):  
Zlatko Janeba ◽  
Antonín Holý ◽  
Milena Masojídková
Keyword(s):  
Hydroxy Group ◽  
Alkyl Derivative ◽  
Reaction Conditions ◽  
Derivatives Of ◽  
Adenine Derivative

Alkylation of 6-amino-7H-purin-8(9H)-thione (8-sulfanyladenine, 1) with one equivalent of (R)-[(trityloxy)methyl]oxirane gave its S-alkyl derivative 2, which was converted to the 6-amino-7H-purin-8(9H)-one (3), while alkylation of 1 with two equivalents of (S)-[(trityloxy)methyl]oxirane afforded a mixture of N3,S-dialkylated product 4a, N9-monoalkyl and N7,N9-dialkyl derivatives of 6-amino-7H-purin-8(9H)-one, 5a and 6a, respectively. This approach can be used for rapid and easy transformation of 8-[(2-hydroxyalkyl)sulfanyl]adenines to the derivatives of 6-amino-7H-purin-8(9H)-one (8-hydroxyadenine) using NaH or Cs2CO3 in DMF. The course of the S→O transformation strictly depends on the character of the starting compounds and on the reaction conditions. N9-Alkyl-8-[(2-hydroxyalkyl)sulfanyl]adenines 10, 12, 14 and 17 were rapidly converted to the corresponding 6-amino-7H-purin-8(9H)-one derivatives 11, 13, 11 and 18, respectively. N9-Unsubstituted 2 reacts slowly, and N3-alkyl derivative 4a is stable under the same reaction conditions. The described transformation does not occur when the hydroxy group in 8-[(2-hydroxyalkyl)sulfanyl]adenine derivative 15 is protected. The reaction using NaH proceeds more rapidly than that using Cs2CO3.

Norbornene in Organic Synthesis

Synthesis ◽  
2018 ◽  
Vol 50 (15) ◽  
pp. 2799-2823 ◽  
Author(s):  
Jianhui Huang ◽  
Caifeng Li ◽  
Liu Liu ◽  
Xuegang Fu
Keyword(s):  
Ring Opening ◽  
Membered Ring ◽  
Ring Formation ◽  
Oxidation Reactions ◽  
Organic Transformations ◽  
Substitution Reactions ◽  
Reaction Conditions ◽  
Multistep Synthesis ◽  
Palladium Catalyzed

The norbornene skeleton possesses an alkene functionality with a fixed conformation, and represents unique reactivity. The use of norbornene and analogues as substrates is overviewed; reactivities are discussed as well as the role of norbornenes as ligands assisting modern organic transformations.1 Introduction2 Synthesis of Substituted Norbornenes2.1 Preparation of Functionalized Norbornenes by Deprotonation and Substitution Reactions2.2 Preparation of Functionalized Norbornenes under Palladium-Catalyzed­ Reaction Conditions2.3 Alkylation of Norbornene2.4 Multistep Synthesis3 Synthesis of Substituted Norbornanes3.1 Three-Membered-Ring Formation3.2 Formation of Four-Membered Rings3.3 Five- and Six-Membered Ring Formation3.4 Syntheses of Difunctionalized Norbornanes4 Synthesis of Cyclopentanes4.1 Oxidation Reactions4.2 Ring-Opening Cross Metathesis (ROCM)4.3 Ring-Opening Metathesis Polymerization (ROMP)4.4 Palladium-Catalyzed Ring-Opening of Norbornene5 Norbornene-Mediated Reactions5.1 Palladium Insertion into Carbon–Halide Bonds5.2 Palladium Insertion into N–H and C–H Bonds5.3 Norbornene as Ligand in Mediated Reactions6 Conclusion

scholarly journals Cyclization into Hydrindanes Using Samarium Diiodide: Stereochemical Features Depending on the Protecting Group

2016 ◽  
Vol 11 (8) ◽  
pp. 1934578X1601100
Author(s):  
Masakazu Sono ◽  
Yukiko Nishibuchi ◽  
Norihito Yamaguchi ◽  
Motoo Tori
Keyword(s):  
Hydroxy Group ◽  
Samarium Diiodide ◽  
Protecting Group ◽  
Reaction Conditions ◽  
Bicyclic Compounds

Monocyclic compounds bearing ketone and enone moieties in the same molecule can be cyclized to bicyclic compounds initiated by samarium diiodide. The stereochemistry of the products depended on the reaction conditions and also the protecting group of the hydroxy group existed in the molecule. A cyclization mechanism is discussed.

scholarly journals Electrochemical oxidation of cholesterol

2015 ◽  
Vol 11 ◽  
pp. 392-402 ◽  
Author(s):  
Jacek W Morzycki ◽  
Andrzej Sobkowiak
Keyword(s):  
Double Bond ◽  
Electrochemical Oxidation ◽  
Hydroxy Group ◽  
Electrophilic Addition ◽  
Side Chain ◽  
Reaction Conditions

Indirect cholesterol electrochemical oxidation in the presence of various mediators leads to electrophilic addition to the double bond, oxidation at the allylic position, oxidation of the hydroxy group, or functionalization of the side chain. Recent studies have proven that direct electrochemical oxidation of cholesterol is also possible and affords different products depending on the reaction conditions.

Undecagold labeling of tRNA

1991 ◽  
Vol 49 ◽  
pp. 44-45
Author(s):  
James F. Hainfeld ◽  
Kyra M. Alford ◽  
Mathias Sprinzl ◽  
Valsan Mandiyan ◽  
Santa J. Tumminia ◽  
...  
Keyword(s):  
High Resolution ◽  
Transmission Electron Micrograph ◽  
Anticodon Loop ◽  
Electron Micrograph ◽  
Reaction Conditions ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

The undecagold (Au11) cluster was used to covalently label tRNA molecules at two specific ribonucleotides, one at position 75, and one at position 32 near the anticodon loop. Two different Au11 derivatives were used, one with a monomaleimide and one with a monoiodacetamide to effect efficient reactions.The first tRNA labeled was yeast tRNAphe which had a 2-thiocytidine (s2C) enzymatically introduced at position 75. This was found to react with the iodoacetamide-Aun derivative (Fig. 1) but not the maleimide-Aun (Fig. 2). Reaction conditions were 37° for 16 hours. Addition of dimethylformamide (DMF) up to 70% made no improvement in the labeling yield. A high resolution scanning transmission electron micrograph (STEM) taken using the darkfield elastically scattered electrons is shown in Fig. 3.

Butenolide ring formation in cardenolide biosynthesis: Spontaneous cyclization of pregnane-21-O-malonyl hemiesters

Planta Medica ◽  
2007 ◽  
Vol 73 (09) ◽  
Author(s):  
RM Pádua ◽  
R Waibel ◽  
SP Kuate ◽  
PK Riedl ◽  
P Gmeiner ◽  
...  
Keyword(s):  
Ring Formation
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