scholarly journals Polar tagging in the synthesis of monodisperse oligo(p-phenyleneethynylene)s and an update on the synthesis of oligoPPEs

2010 ◽  
Vol 6 ◽  
Author(s):  
Dhananjaya Sahoo ◽  
Susanne Thiele ◽  
Miriam Schulte ◽  
Navid Ramezanian ◽  
Adelheid Godt
Keyword(s):  
Chromatographic Separation ◽  
Side Reaction ◽  
Building Blocks ◽  
Protecting Groups ◽  
Side Chains ◽  
Protecting Group ◽  
Synthetic Route ◽  
End Groups ◽  
Pure Compounds ◽  
Better Than

One important access to monodisperse (functionalized) oligoPPEs is based on the orthogonality of the alkyne protecting groups triisopropylsilyl and hydroxymethyl (HOM) and on the polar tagging with the hydroxymethyl moiety for an easy chromatographic separation of the products. This paper provides an update of this synthetic route. For the deprotection of HOM protected alkynes, γ-MnO2 proved to be better than (highly) activated MnO2. The use of HOM as an alkyne protecting group is accompanied by carbometalation as a side reaction in the alkynyl–aryl coupling. The extent of carbometalation can be distinctly reduced through substitution of HOM for 1-hydroxyethyl. The strategy of polar tagging is extended by embedding ether linkages within the solubilising side chains. With building blocks such as 1,4-diiodo-2,5-bis(6-methoxyhexyl) less steps are needed to assemble oligoPPEs with functional end groups and the isolation of pure compounds becomes simple. For the preparation of 1,4-dialkyl-2,5-diiodobenzene a better procedure is presented together with the finding that 1,4-dialkyl-2,3-diiodobenzene, a constitutional isomer of 1,4-dialkyl-2,5-diiodobenzene, is one of the byproducts.

scholarly journals Revisiting NO2 as Protecting Group of Arginine in Solid-Phase Peptide Synthesis

2020 ◽  
Vol 21 (12) ◽  
pp. 4464
Author(s):  
Mahama Alhassan ◽  
Ashish Kumar ◽  
John Lopez ◽  
Fernando Albericio ◽  
Beatriz G. de la Torre
Keyword(s):  
Peptide Synthesis ◽  
Solid Phase ◽  
Solid Phase Peptide Synthesis ◽  
Side Reaction ◽  
Reducing Agent ◽  
Protecting Groups ◽  
Side Chain ◽  
Protecting Group ◽  
Mild Acid

The protection of side-chain arginine in solid-phase peptide synthesis requires attention since current protecting groups have several drawbacks. Herein, the NO2 group, which is scarcely used, has been revisited. This work shows that it prevents the formation of δ-lactam, the most severe side-reaction during the incorporation of Arg. Moreover, it is stable in solution for long periods and can be removed in an easy-to-understand manner. Thus, this protecting group can be removed while the protected peptide is still anchored to the resin, with SnCl2 as reducing agent in mild acid conditions using 2-MeTHF as solvent at 55 °C. Furthermore, we demonstrate that sonochemistry can facilitate the removal of NO2 from multiple Arg-containing peptides.

scholarly journals Synthesis of 4-Substituted-1,2-Dihydroquinolines by Means of Gold-Catalyzed Intramolecular Hydroarylation Reaction of N-Ethoxycarbonyl-N-Propargylanilines

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3366
Author(s):  
Antonio Arcadi ◽  
Andrea Calcaterra ◽  
Giancarlo Fabrizi ◽  
Andrea Fochetti ◽  
Antonella Goggiamani ◽  
...  
Keyword(s):  
Building Blocks ◽  
Fine Tuning ◽  
Para Position ◽  
Cyclization Product ◽  
Synthetic Route ◽  
Substituted Anilines ◽  
Novel Approach ◽  
High Yields

An alternative Au(I)-catalyzed synthetic route to functionalized 1,2-dihydroquinolines is reported. This novel approach is based on the use of N-ethoxycarbonyl protected-N-propargylanilines as building blocks that rapidly undergo the IMHA reaction affording the 6-endo cyclization product in good to high yields. In the presence of N-ethoxycarbonyl-N-propargyl-meta-substituted anilines, the regiodivergent cyclization at the ortho-/para-position is achieved by the means of catalyst fine tuning.

Synthesis of sp3-Enriched β-Fluoro Sulfonyl Chlorides

Synthesis ◽  
2020 ◽  
Author(s):  
Oleksandr O. Grygorenko ◽  
Rustam Gurbanov ◽  
Andriy Sokolov ◽  
Sergey Golovach ◽  
Kostiantyn Melnykov ◽  
...  
Keyword(s):  
Drug Discovery ◽  
Double Bond ◽  
Building Blocks ◽  
Protecting Groups ◽  
Sulfonyl Chlorides ◽  
Wide Range ◽  
Cyclic Compounds

AbstractA three-step approach to the synthesis of sp3-enriched β-fluoro sulfonyl chlorides starting from alkenes is reported. The method was successfully applied to a wide range of acyclic and cyclic substrates, bearing either an exocyclic or an endocyclic double bond. The procedure worked with a wide range of substrates and tolerated a number of functional and protecting groups. Moreover, the target cyclic compounds were obtained as single cis diastereomers on a multigram scale. The title compounds are promising building blocks for drug discovery that can be used to obtain sp3-enriched β-fluoro and α,β-unsaturated sulfonamides.

scholarly journals A Building-Block-Based Genetic Algorithm for Solving the Robots Allocation Problem in a Robotic Mobile Fulfilment System

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Jingtian Zhang ◽  
Fuxing Yang ◽  
Xun Weng
Keyword(s):  
Genetic Algorithm ◽  
Dynamic Scheduling ◽  
Building Blocks ◽  
Allocation Problem ◽  
Accurate Analysis ◽  
Allocation Problems ◽  
Scheduling Method ◽  
Project Scheduling Problem ◽  
Block Based ◽  
Better Than

Robotic mobile fulfilment system (RMFS) is an efficient and flexible order picking system where robots ship the movable shelves with items to the picking stations. This innovative parts-to-picker system, known as Kiva system, is especially suited for e-commerce fulfilment centres and has been widely used in practice. However, there are lots of resource allocation problems in RMFS. The robots allocation problem of deciding which robot will be allocated to a delivery task has a significant impact on the productivity of the whole system. We model this problem as a resource-constrained project scheduling problem with transfer times (RCPSPTT) based on the accurate analysis of driving and delivering behaviour of robots. A dedicated serial schedule generation scheme and a genetic algorithm using building-blocks-based crossover (BBX) operator are proposed to solve this problem. The designed algorithm can be combined into a dynamic scheduling structure or used as the basis of calculation for other allocation problems. Experiment instances are generated based on the characteristics of RMFS, and the computation results show that the proposed algorithm outperforms the traditional rule-based scheduling method. The BBX operator is rapid and efficient which performs better than several classic and competitive crossover operators.

scholarly journals Propargyloxycarbonyl as a protecting group for the side chains of serine, threonine and tyrosine

2008 ◽  
Vol 120 (1) ◽  
pp. 163-173 ◽  
Author(s):  
Ramapanicker Ramesh ◽  
Kavita De ◽  
Shipra Gupta ◽  
Srinivasan Chandrasekaran
Keyword(s):  
Side Chains ◽  
Protecting Group

scholarly journals The Efficient Synthesis of Azasugars from Pentoses

2021 ◽  
Author(s):  
◽  
Michael Meijlink
Keyword(s):  
Clinical Trials ◽  
Biological Properties ◽  
Protecting Groups ◽  
Synthetic Route ◽  
Efficient Synthesis ◽  
Atom Economy ◽  
Total Syntheses ◽  
Structural Analogues ◽  
Original Procedure ◽  
Synthetic Routes

<p>Azasugars [e.g., 1-deoxy-aza-xylopyranose (1) Figure 1] are structural analogues of sugars [e.g., α-D-xylopyranose (2)] where the ring oxygen is substituted by a nitrogen atom. The resemblance of azasugars to their carbohydrate counterparts gives them various biological properties, such as the inhibition of glycosidase and glycosyltransferase enzymes, and as such, these compounds have been in clinical trials for the treatment of AIDS, diabetes,and cancer. Synthetic routes to azasugars have often involved the use of protecting groups, and therefore have generally reduced efficiency by requiring additional steps to apply or remove protecting groups or requiring adjustment of stereochemistry during the synthesis. This thesis presents the first example of a synthesis of four sterochemically different piperidine triols through a four-step methodology minimising the use of protecting groups starting from pentoses. The synthesis of D-xylose derived (3R,4r,5S)-piperidine triol was previously obtained in 40% yield over five steps, but was afforded in 45% overall yield over four steps using the methodology described within this thesis. Next, D-ribose derived (3R,4s,5S)-piperidine triol was obtained in 40% overall yield over four steps, which afforded a vast improvement on the previous most efficient synthetic route obtaining the azasugar in 24% yield over four steps. This four-step three-pot methodology has thus allowed for the synthesis of these piperidine triols in overall yields ranging from 4-69%, surpassing previous total syntheses in efficiency and improving overall atom economy. To further probe the applicability of the methodology, N-alkyl analogues (such as butyl-, phenylethyl-, and hydroxyethyl-analogues) of all four different piperidine triols were synthesised in comparable or greater overall yields compared to literature reports without any required adaptation to the original procedure. Included in these N-alkyl analogues are seven novel azasugars which were obtained in overall yields ranging from 6-35%.</p>

Efficient synthesis of polysubstituted 1,5-benzodiazepinone dipeptide mimetics via an Ugi-4CR-Ullmann condensation sequence

Synlett ◽  
2021 ◽  
Author(s):  
Robin Van Den Hauwe ◽  
Mathias Elsocht ◽  
Charlie Hollanders ◽  
Steven Ballet
Keyword(s):  
Building Blocks ◽  
Synthetic Route ◽  
Efficient Synthesis ◽  
Rapid Construction ◽  
Ligand Free

An efficient three step synthesis towards 3-amino-1,4-benzodiazepin-2-one derivatives is presented. The versatile Ugi-4-component reaction (Ugi-4CR) and Boc-deprotection is followed by a ligand-free Ullmann condensation. This protocol allows the rapid construction of a diverse array of substituted 1,5-benzodiazepinones. Since Ugi-based products are typically limited by their ‘inert’ C-terminal amides, the use of a convertible (‘cleavable’) isocyanide was envisaged and resulted in building blocks that can be made SPPS-compatible. To demonstrate the potential of this novel synthetic route, the design and preparation of novel phenylurea-1,5-bezondiazepin-4(5H)-one dipeptide mimetics with potential CCK2-antagonist properties is reported.

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.

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