Synthetic Versatility of Lipases: Application for Si–O Bond Formation and Cleavage

Synthesis ◽  
2018 ◽  
Vol 51 (02) ◽  
pp. 477-485 ◽  
Author(s):  
Patrícia Brondani ◽  
Mateus Mittersteiner ◽  
Morgana Voigt ◽  
Bruna Klinkowski ◽  
Dilamara Riva Scharf ◽  
...  
Keyword(s):  
Room Temperature ◽  
Bond Formation ◽  
Inert Atmosphere ◽  
Protecting Groups ◽  
Silyl Ether ◽  
Secondary Alcohols ◽  
Protecting Group ◽  
Silyl Ethers ◽  
Dry Conditions ◽  
Silicon Based

Several commercially available lipases were examined in a study on O–Si bond formation and cleavage applying silicon-based protecting groups and alcohols or the corresponding silyl ethers. With regard to deprotection, from silyl ether to the corresponding alcohol, only the solvent and the lipase were necessary. The influence of the protecting group, the lipase source, and the substituent was investigated to optimize the results. The TMS moiety could be removed in 24 hours of reaction at room temperature in aqueous systems (conv. up to 99%, depending on the substrate and lipase). The reverse reactions, that is, with the protection of the alcohols, were carried out in hexane using different silyl chlorides. The TMS, TES, and TBS moieties were successfully inserted in the primary and secondary alcohols without the need for dry conditions or an inert atmosphere, presenting conversions of up to 99%, depending on the substrate.

Protecting Groups

2008 ◽  
Author(s):  
Jie Jack Li ◽  
Chris Limberakis ◽  
Derek A. Pflum
Keyword(s):  
Low Temperature ◽  
Organic Synthesis ◽  
Secondary Alcohol ◽  
Primary Alcohol ◽  
Protecting Groups ◽  
Silyl Ether ◽  
Benzyl Ether ◽  
Protecting Group ◽  
Selective Protection ◽  
Death Taxes

In his book, Protecting Groups, Philip J. Kocieński stated that there are three things that cannot be avoided: death, taxes, and protecting groups. Indeed, protecting groups mask functionality that would otherwise be compromised or interfere with a given reaction, making them a necessity in organic synthesis. In this chapter, for each protecting group showcased, only the most widely used methods for protection and cleavage are shown. Also, this section is not comprehensive and only addresses some of the most common blocking groups in organic synthesis. For a thorough review of protecting groups, the reader should consult the following references: (a) Wuts, P. G. M.; Greene, T. W.; Protective Groups in Organic Synthesis, 4th ed.; Wiley: Hoboken, NJ, 2007; (b) Kocienski, P. J. Protecting Groups, 3rd edition.; Thieme: Stuggart, 2004. In this section, the formation and cleavage of eight protecting groups for alcohols and phenols are presented: acetate; acetonides for diols; benzyl ether; para-methoxybenzyl (PMB) ether; methyl ether; methoxymethylene (MOM) ether; tert-butyldiphenylsilyl (TBDPS) silyl ether; and tetrahydropyran (THP). Acetate is a convenient protecting group for alcohols—easy on and easy off. Selective protection of a primary alcohol in the presence of a secondary alcohol can be achieved at low temperature. The drawback of this protecting group is its incompatibility with hydrolysis and reductive conditions.

scholarly journals An Expeditious, Green and Protecting-Group-Free Synthesis of a Potent Secondary Metabolite Calebin-A and Its Analogues

SynOpen ◽  
2017 ◽  
Vol 01 (01) ◽  
pp. 0125-0128 ◽  
Author(s):  
Anju Majeed ◽  
Kalyanam Nagabhushanam ◽  
Muhammed Majeed ◽  
Samuel Thomas ◽  
Nooruddin Thajuddin
Keyword(s):  
Secondary Metabolite ◽  
Room Temperature ◽  
Curcuma Longa ◽  
Protecting Groups ◽  
Protecting Group ◽  
Active Components ◽  
Water Solvent ◽  
Biphasic Medium ◽  
Pharmacologically Active ◽  
Neutral Conditions

The synthesis of Calebin-A (10a) and analogues (10b–d), which are minor but pharmacologically active components (<0.01% of the oleoresin) of curcuma longa, is described. This flexible synthesis is achieved under near neutral conditions in water/solvent biphasic medium at room temperature without involving any protecting groups.

Recent Advances on C-Se Bond-forming Reactions at Low and Room Temperature

2020 ◽  
Vol 23 (28) ◽  
pp. 3206-3225 ◽  
Author(s):  
Amol D. Sonawane ◽  
Mamoru Koketsu
Keyword(s):  
Room Temperature ◽  
Bond Formation ◽  
Bond Forming ◽  
Material Chemistry ◽  
Recent Advances ◽  
Bond Forming Reactions ◽  
Bond Formation Reactions

: Over the last decades, many methods have been reported for the synthesis of selenium- heterocyclic scaffolds because of their interesting reactivities and applications in the medicinal as well as in the material chemistry. This review describes the recent numerous useful methodologies on C-Se bond formation reactions which were basically carried out at low and room temperature.

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.

On the Chemistry of Ingenol, III [1] Synthesis of 3-Deoxy-3-oxoingenol, Some 5-Esters and of Ethers and Acetals of Ingenol

1982 ◽  
Vol 37 (12) ◽  
pp. 1640-1647 ◽  
Author(s):  
Bernd Sorg ◽  
Erich Hecker
Keyword(s):  
Good Yield ◽  
Protecting Groups ◽  
Silyl Ether ◽  
Subsequent Removal ◽  
Mouse Ear

3-Deoxy-3-oxoingenol (3) was prepared from ingenol-5,20-acetonide (25) by oxidation and subsequent removal of the acetonide. 3 was acylated to give homologous 5,20-diacylates 5-9. From these the 5-monoacylates 14, 15 and 17 were obtained in only moderate yields. Therefore the 20-silyl ether 10 (prepared from 3) was acylated. After smooth removal of the silyl ether the homologous 5-acylates 16. 18 and 19 resulted in good yield. The 5,20-dibutyrate 6 and all 5-acylates prepared (14-19) showed no irritant activity on the mouse ear. The 3-oxo-5-acylates 14-19 could not be reduced to give ingenol-5-acylates (24). Therefore various ingenol derivatives, 29-32, with suitable protected hydroxyl functions as well as the corresponding 5-clecanoates 35-38 were synthesized. The protecting groups of the derivatives 35-38 could however not be cleaved off to yield ingenol-5- decanoate (24)

The remarkable catalytic activity of ultra-small free-CeO2 nanoparticles in selective carbon–carbon bond formation reactions in water at room temperature

2015 ◽  
Vol 39 (7) ◽  
pp. 5350-5353 ◽  
Author(s):  
Subhash Banerjee
Keyword(s):  
Catalytic Activity ◽  
Room Temperature ◽  
Bond Formation ◽  
Ceo2 Nanoparticles ◽  
Cerium Oxide Nanoparticles ◽  
Oxide Nanoparticles ◽  
Reusable Catalyst ◽  
Carbon Carbon Bond ◽  
Active Methylene Compounds ◽  
Active Methylene

A simple and efficient protocol for selective bis-Michael addition and mono-allylation of active methylene compounds has been demonstrated using ultra-small size (∼5 nm) uncapped cerium oxide nanoparticles (free-CeO2 NPs) as a reusable catalyst in water at room temperature.

Alkene Difunctionalization Directed by Free Amines: Diamine Synthesis via Nickel-Catalyzed 1,2-Carboamination

2021 ◽  
Author(s):  
Taeho Kang ◽  
José Manuel González ◽  
Zi-Qi Li ◽  
Klement Foo ◽  
Peter Cheng ◽  
...  
Keyword(s):  
Nickel Catalyst ◽  
Room Temperature ◽  
Kinetic Studies ◽  
Fine Tuning ◽  
Secondary Amines ◽  
Protecting Group ◽  
Wide Range ◽  
Leaving Group ◽  
Primary And Secondary Amines ◽  
Reaction Proceeds

A versatile method to access differentially substituted 1,3- and 1,4-diamines via a nickel-catalyzed three-component 1,2-carboamination of alkenyl amines with aryl/alkenylboronic ester nucleophiles and N–O electrophiles is reported. The reaction proceeds efficiently with free primary and secondary amines without needing a directing auxiliary or protecting group, and is enabled by fine-tuning the leaving group on the N–O reagent. The transformation is highly regioselective and compatible with a wide range of coupling partners and alkenyl amine substrates, all performed at room temperature. A series of kinetic studies support a mechanism in which alkene coordination to the nickel catalyst is turnover-limiting.

Green Amide Bond Formation in Water via Direct Coupling of Metal Carboxylate Salts with Ammonium Salts at Room Temperature

2021 ◽  
Author(s):  
Truong Thanh Tung ◽  
John Nielsen
Keyword(s):  
Room Temperature ◽  
Bond Formation ◽  
Direct Coupling ◽  
Ammonium Salts ◽  
Amide Bond ◽  
Metal Carboxylate ◽  
Amide Bond Formation ◽  
Simple Protocol

Herein, we report the green, expedite, and practically simple protocol for direct coupling of carboxylate salts and ammonium salts under ACN/H2O conditions at room temperature without the addition of tertiary...

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