scholarly journals Application of the N-Dibenzyl Protective Group in the Preparation of β-Lactam Pseudopeptides

Molecules ◽  
2019 ◽  
Vol 24 (7) ◽  
pp. 1261
Author(s):  
Rok Frlan ◽  
Martina Hrast ◽  
Stanislav Gobec
Keyword(s):  
Mitsunobu Reaction ◽  
Successful Implementation ◽  
Protective Group ◽  
Reaction Conditions ◽  
Protective Groups ◽  
High Yields ◽  
Synthetic Approaches

Despite the great importance of β-lactam antibiotics, there is still a limited number of synthetic approaches for the formation of β-lactam–containing dipeptides. In this study, we report upon the stereoselective preparation of β-lactam–containing pseudopeptides, where different reaction conditions and NH2 protective groups were tested to obtain compounds that contain 3-amino-azetidin-2-one. We demonstrate that the protective group is essential for the outcome of the reaction. Successful implementation of dibenzyl-protected serine-containing dipeptides through the Mitsunobu reaction can provide the desired products at high yields and stereoselectivity.

Azidation of Partially Protected Carbohydrate Derivatives: Efficient Suppression of Acyl Migration

Synlett ◽  
2020 ◽  
Vol 31 (15) ◽  
pp. 1491-1496
Author(s):  
Leonid O. Kononov ◽  
Elena V. Stepanova ◽  
Alexander I. Zinin ◽  
Polina I. Abronina ◽  
Alexander O. Chizhov
Keyword(s):  
Organic Chemistry ◽  
Phase Transfer ◽  
Acyl Migration ◽  
Hydroxyl Group ◽  
Azido Group ◽  
Protective Group ◽  
Reaction Conditions ◽  
Free Hydroxy Group ◽  
Efficient Suppression ◽  
Protective Groups

Although azidation by nucleophilic substitution is widely used in organic chemistry, it has a limitation for partially protected carbohydrate derivatives under typical reaction conditions used for azidation (heating with NaN3, phase-transfer catalyst (optional), DMF or DMSO) as it can cause substantial migration (70%) of O-acyl protective groups. Several approaches, including the use of a temporary protective group for the unprotected hydroxyl group, to avoid acyl migration have been compared. Addition of excess of ethyl trifluroacetate effectively suppressed benzoyl migration but inhibited substitution of the chlorine atom with the azido group. The most robust procedure involved addition of excess n-butyl formate to the reaction mixture. When this protocol was followed, migration of benzoyl groups in lactose derivatives with free hydroxy group at C-3′ or C-4′ was reduced to 4%, with the yield of the target, partially protected derivatives with an azido group in the aglycone approaching 92%.

Aptamer protective groups tolerate different reagents and reactions for regioselective modification of neomycin B

2020 ◽  
Vol 18 (47) ◽  
pp. 9606-9610
Author(s):  
Andreas A. Bastian ◽  
Agnieszka Gruszka ◽  
Philippe Jung ◽  
Andreas Herrmann
Keyword(s):  
Protective Group ◽  
Reaction Conditions ◽  
Group Strategy ◽  
Protective Groups ◽  
Neomycin B ◽  
Regioselective Modification

The aptameric protective group strategy is compatible with diverse reagents and reaction conditions for the synthesis of new neomycin B derivatives.

A Facile, Efficient and Selective Deprotection of P - Methoxy Benzyl Ethers Using Zinc (II) Trifluoromethanesulfonate

2019 ◽  
Vol 16 (12) ◽  
pp. 955-958
Author(s):  
Reddymasu Sireesha ◽  
Reddymasu Sreenivasulu ◽  
Choragudi Chandrasekhar ◽  
Mannam Subba Rao
Keyword(s):  
Room Temperature ◽  
Protecting Groups ◽  
Side Reactions ◽  
Reaction Conditions ◽  
Acid Sensitivity ◽  
Time Period ◽  
Protective Groups ◽  
Benzyl Ethers ◽  
Last Stage ◽  
Zinc Triflate

: Deprotection is significant and conducted over mild reaction conditions, in order to restrict any more side reactions with sensitive functional groups as well as racemization or epimerization of stereo center because the protective groups are often cleaved at last stage in the synthesis. P - Methoxy benzyl (PMB) ether appears unique due to its easy introduction and removal than the other benzyl ether protecting groups. A facile, efficient and highly selective cleavage of P - methoxy benzyl ethers was reported by using 20 mole% Zinc (II) Trifluoromethanesulfonate at room temperature in acetonitrile solvent over 15-120 min. time period. To study the generality of this methodology, several PMB ethers were prepared from a variety of substrates having different protecting groups and subjected to deprotection of PMB ethers using Zn(OTf)2 in acetonitrile. In this methodology, zinc triflate cleaves only PMB ethers without affecting acid sensitivity, base sensitivity and also chiral epoxide groups.

Novel One-pot Synthesis of Pyranocarbazole Derivatives via an Isocyanide-based Three-component Reaction

2020 ◽  
Vol 17 ◽  
Author(s):  
Visarapu Malathi ◽  
Pedavenkatagari Narayana Reddy ◽  
Pannala Padmaja
Keyword(s):  
Efficient Method ◽  
Atom Economy ◽  
Reaction Conditions ◽  
One Pot ◽  
Catalyst Free ◽  
One Pot Synthesis ◽  
Three Component Reaction ◽  
High Yields

Abstract:: An efficient method has been developed for the synthesis of new pyrano[3,2-c] and pyrano[3,2-a]carbazole de-rivatives via a three component reaction of 4-hydroxycarbazole or 2-hydroxycarbazole, isocyanides, and dialkylacetylenedi-carboxylates. Noteworthy features of this protocol include mild reaction conditions, catalyst-free, high atom-economy and high yields.

scholarly journals Applications of the Horner-Wadsworth-Emmons olefination in modern natural product synthesis

Synthesis ◽  
2021 ◽  
Author(s):  
Dávid Roman ◽  
Maria Sauer ◽  
Christine Beemelmanns
Keyword(s):  
Natural Products ◽  
Natural Product ◽  
Natural Product Synthesis ◽  
Reaction Conditions ◽  
Comprehensive Review ◽  
Modern Natural ◽  
Key Steps ◽  
Synthetic Approaches

Here, we have summarized more than 30 representative natural product syntheses published in 2015 to 2020 that employ one or more Horner-Wadsworth-Emmons (HWE) reactions. We comprehensively describe the applied phosphonate reagents, HWE reaction conditions and key steps of the total synthetic approaches. Our comprehensive review will support future synthetic approaches and serve as guideline to find the best HWE conditions for the most complicated natural products known

scholarly journals A two step synthesis of a key unit B precursor of cryptophycins by asymmetric hydrogenation

2011 ◽  
Vol 7 ◽  
pp. 243-245 ◽  
Author(s):  
Benedikt Sammet ◽  
Mathilde Brax ◽  
Norbert Sewald
Keyword(s):  
Asymmetric Hydrogenation ◽  
Synthetic Route ◽  
Reaction Conditions ◽  
High Yields

A novel highly enantioselective two step access to a unit B precursor of cryptophycins in good yields from commercially available starting materials has been developed. The key step is an asymmetric hydrogenation using the commercially available [(COD)Rh-(R,R)-Et-DuPhos]BF4 catalyst. The synthetic route provides the advantage of less synthetic steps, proceeds with high yields and enantioselectivity, and avoids hazardous reaction conditions.

scholarly journals A Simple and Efficient Synthesis of Highly Substituted Indeno[1,2-b]pyrrole and Acenaphtho[1,2-b]pyrrole Derivatives by Tandem Three-Component Reactions

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 3031 ◽  
Author(s):  
Xiaodong Tang ◽  
Songlei Zhu ◽  
Ying Ma ◽  
Ren Wen ◽  
Lanqi Cen ◽  
...  
Keyword(s):  
Environmentally Benign ◽  
Efficient Synthesis ◽  
Reaction Conditions ◽  
Dicarbonyl Compounds ◽  
Pyrrole Derivatives ◽  
Three Component Reaction ◽  
High Yields ◽  
Operational Simplicity

A green, convenient and tandem procedure for the efficient synthesis of highly substituted indeno[1,2-b]pyrrole and acenaphtho[1,2-b]pyrrole derivatives by domino three-component reaction of tryptamine/benzylamine, 1,3-dicarbonyl compounds and ninhydrin/ acenaphthenequinone is described. The significant features of this procedure were characterized by mild reaction conditions, high yields, operational simplicity and it being environmentally benign.

scholarly journals New opportunities in the stereoselective dearomatization of indoles

2016 ◽  
Vol 88 (3) ◽  
pp. 207-214 ◽  
Author(s):  
Elisabetta Manoni ◽  
Assunta De Nisi ◽  
Marco Bandini
Keyword(s):  
Acid Catalysis ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Reaction Conditions ◽  
Brönsted Acid ◽  
High Yields ◽  
First Time ◽  
Tailored Design ◽  
Bronsted Acid Catalysis

AbstractThe regio- and stereoselective dearomatization of indoles is realized for the first time by combining readily available indolyl precursors and electron-rich allenes, namely allenamides and aryloxyallenes. Inter- as well as intramolecular condensations were realized under gold and Brønsted acid catalysis providing a range of densely functionalized indoline and indolenine cores in high yields and excellent stereochemical outcome. Chemodivergent reaction profiles (Micheal-type addition vs. [2+2]-cycloaddition) were realized by a tailored design of both reaction conditions and functionalization of the reaction partners.

Synthesis of 4-arylethyl-6-arylpyrimidine-2-thiols through aza-Michael addition/nucleophilic addition/aromatization tandem reactions

2018 ◽  
Vol 24 (1) ◽  
pp. 23-26
Author(s):  
Zheng Li ◽  
Wenli Song ◽  
Jiaojiao He ◽  
Yan Du ◽  
Jingya Yang
Keyword(s):  
Efficient Method ◽  
Michael Addition ◽  
Nucleophilic Addition ◽  
Tandem Reactions ◽  
Reaction Conditions ◽  
High Yields ◽  
Work Up

Abstract An efficient method for the synthesis of the title compounds by reactions of divinyl ketones with thiourea is described. This protocol has the advantages of high yields, mild reaction conditions and simple work-up procedure.

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