scholarly journals A model study of epothilone synthesis: An alternative synthetic approach to the C1-C7 fragment

2002 ◽  
Vol 67 (4) ◽  
pp. 221-228 ◽  
Author(s):  
Gojko Lalic ◽  
Danica Galonic ◽  
Radomir Matovic ◽  
Radomir Saicic
Keyword(s):  
Synthetic Approach ◽  
Protective Group ◽  
Reaction Sequence ◽  
Reaction Conditions ◽  
Model Study

In this model study an alternative synthetic approach to the C1?C7 fragment of epothilones was investigated. Starting from 4,4-dimethylcyclopentenone, a 7 step reaction sequence afforded the key intermediate 7 in 27% overall yield. Surprisingly, the attempted deprotection of latent functionalities in 7 failed, indicating the incompatibility of the ethoxyethyl protective group with the reaction conditions employed.

A Synthesis of 2-Amino-2,6-dideoxy-D-(and L-)galaetose (Fucosamine) and 2-Amino-2,6-dideoxy-D-(and L-)talose (Pneumosamine)

1973 ◽  
Vol 51 (6) ◽  
pp. 974-977 ◽  
Author(s):  
Malcolm B. Perry ◽  
Virginia Daoust
Keyword(s):  
Similar Reaction ◽  
Reaction Sequence ◽  
Reaction Conditions ◽  
Nef Reaction ◽  
Methanolic Ammonia

5-Deoxy-D-lyxose underwent base-catalyzed addition with nitromethane to give a mixture of 1,6-dideoxy-1-nitro-D-galactitol and 1,6-dideoxy-1-nitro-D-talitol (ca. 2:1). Acetylation of the crystalline 1,6-dideoxy-1-nitro-D-galactitol gave 2,3,4,5-tetra-O-acetyl-1,6-dideoxy-1-nitro-D-galactitol which on treatment with methanolic ammonia afforded 2-acetamido-1,2,6-trideoxy-1-nitro-D-talitol and 2-acetamido-1,2,6-trideoxy-1-nitro-D-galactitol (ca. 3:1) which under the modified Nef reaction conditions gave 2-acetamido-2,6-dideoxy-D-talose and 2-acetamido-2,6-dideoxy-D-galactose respectively. The glycoses were converted to 2-amino-2,6-dideoxy-D-talose hydrochloride and 2-amino-2,6-dideoxy-D-galactose hydrochloride on hydrolysis with hydrochloric acid.A similar reaction sequence applied to 5-deoxy-L-lyxose afforded the L-enantiomorphic intermediates, and gave 2-amino-2,6-dideoxy-L-talose hydrochloride and 2-amino-2,6-dideoxy-L-galactose hydrochloride as final products.

scholarly journals Appel-reagent-mediated transformation of glycosyl hemiacetal derivatives into thioglycosides and glycosyl thiols

2013 ◽  
Vol 9 ◽  
pp. 974-982 ◽  
Author(s):  
Tamashree Ghosh ◽  
Abhishek Santra ◽  
Anup Kumar Misra
Keyword(s):  
Reaction Sequence ◽  
Reaction Conditions ◽  
One Pot ◽  
Carbon Tetrabromide

A series of glycosyl hemiacetal derivatives have been transformed into thioglycosides and glycosyl thiols in a one-pot two-step reaction sequence mediated by Appel reagent (carbon tetrabromide and triphenylphosphine). 1,2-trans-Thioglycosides and β-glycosyl thiol derivatives were stereoselectively formed by the reaction of the in situ generated glycosyl bromides with thiols and sodium carbonotrithioate. The reaction conditions are reasonably simple and yields were very good.

Diversity-Oriented Synthesis via Catalyst-Free Addition of Ketones to [e]-Fused 1H-Pyrrole-2,3-diones

Synthesis ◽  
2018 ◽  
Vol 50 (24) ◽  
pp. 4897-4904 ◽  
Author(s):  
Ekaterina Stepanova ◽  
Andrey Maslivets ◽  
Svetlana Kasatkina ◽  
Maksim Dmitriev
Keyword(s):  
Intramolecular Cyclization ◽  
Aromatic Hydrocarbons ◽  
Michael Addition ◽  
Aldol Reaction ◽  
Synthetic Approach ◽  
Reaction Conditions ◽  
Diversity Oriented Synthesis ◽  
Catalyst Free ◽  
Solvent Free Conditions ◽  
Reaction Proceeds

A facile synthetic approach towards two distinct pyrrole-based heterocyclic scaffolds has been developed by the interaction of 1H-pyrrole-2,3-diones fused at the [e]-side to a 1,4-benzoxazin-2-one or quinoxalin-2(1H)-one moiety with ketones. The described interaction proceeds either as an aldol reaction or as a Michael addition/intramolecular cyclization depending on the reaction conditions. The disclosed aldol reaction proceeds with good diastereoselectivity under catalyst-free conditions when the reaction is carried out in aromatic hydrocarbons. Products of the cascade Michael addition/intramolecular cyclization reaction are predominantly formed under catalyst-free and solvent-free conditions. The proposed strategy provides facile access to pharmaceutically interesting pyrrole-based polyheterocycles.

scholarly journals A selective and mild glycosylation method of natural phenolic alcohols

2016 ◽  
Vol 12 ◽  
pp. 524-530 ◽  
Author(s):  
Mária Mastihubová ◽  
Monika Poláková
Keyword(s):  
Synthetic Approach ◽  
Reaction Sequence ◽  
Simple Reaction ◽  
Glycoside Synthesis ◽  
Highly Efficient ◽  
Phenolic Alcohols

Several bioactive natural p-hydroxyphenylalkyl β-D-glucopyranosides, such as vanillyl β-D-glucopyranoside, salidroside and isoconiferin, and their glycosyl analogues were prepared by a simple reaction sequence. The highly efficient synthetic approach was achieved by utilizing acetylated glycosyl bromides as well as aromatic moieties and mild glycosylation promoters. The aglycones, p-O-acetylated arylalkyl alcohols, were prepared by the reduction of the corresponding acetylated aldehydes or acids. Various stereoselective 1,2-trans-O-glycosylation methods were studied, including the DDQ–iodine or ZnO–ZnCl2 catalyst combination. Among them, ZnO–iodine has been identified as a new glycosylation promoter and successfully applied to the stereoselective glycoside synthesis. The final products were obtained by conventional Zemplén deacetylation.

scholarly journals Integrated and Metal Free Synthesis of Dimethyl Carbonate and Glycidol from Glycerol Derived 1,3-Dichloro-2-propanol via CO2 Capture

2021 ◽  
Vol 3 (4) ◽  
pp. 685-698
Author(s):  
Santosh Khokarale ◽  
Ganesh Shelke ◽  
Jyri-Pekka Mikkola
Keyword(s):  
Co2 Capture ◽  
Dimethyl Carbonate ◽  
Chemical Species ◽  
Cyclic Carbonate ◽  
Chloride Ions ◽  
Synthetic Approach ◽  
Integrated Process ◽  
Reaction Conditions ◽  
Metal Free ◽  
Analysis Technique

Dimethyl carbonate (DMC) and glycidol are considered industrially important chemical entities and there is a great benefit if these moieties can be synthesized from biomass-derived feedstocks such as glycerol or its derivatives. In this report, both DMC and glycidol were synthesized in an integrated process from glycerol derived 1,3-dichloro-2-propanol and CO2 through a metal-free reaction approach and at mild reaction conditions. Initially, the chlorinated cyclic carbonate, i.e., 3-chloro-1,2-propylenecarbonate was synthesized using the equivalent interaction of organic superbase 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) and 1,3-dichloro-2-propanol with CO2 at room temperature. Further, DMC and glycidol were synthesized by the base-catalyzed transesterification of 3-chloro-1,2-propylenecarbonate using DBU in methanol. The synthesis of 3-chloro-1,2-propylenecarbonate was performed in different solvents such as dimethyl sulfoxide (DMSO) and 2-methyltetrahydrofuran (2-Me-THF). In this case, 2-Me-THF further facilitated an easy separation of the product where a 97% recovery of the 3-chloro-1,2-propylenecarbonate was obtained compared to 63% with DMSO. The use of DBU as the base in the transformation of 3-chloro-1,2-propylenecarbonate further facilitates the conversion of the 3-chloro-1,2 propandiol that forms in situ during the transesterification process. Hence, in this synthetic approach, DBU not only eased the CO2 capture and served as a base catalyst in the transesterification process, but it also performed as a reservoir for chloride ions, which further facilitates the synthesis of 3-chloro-1,2-propylenecarbonate and glycidol in the overall process. The separation of the reaction components proceeded through the solvent extraction technique where a 93 and 89% recovery of the DMC and glycidol, respectively, were obtained. The DBU superbase was recovered from its chlorinated salt, [DBUH][Cl], via a neutralization technique. The progress of the reactions as well as the purity of the recovered chemical species was confirmed by means of the NMR analysis technique. Hence, a single base, as well as a renewable solvent comprising an integrated process approach was carried out under mild reaction conditions where CO2 sequestration along with industrially important chemicals such as dimethyl carbonate and glycidol were synthesized.

An unusual tert-butylamine mediated conversion of 6-aryl-7-formyl-2,4,5,8-tetrahydro-1,3-dioxa-5-azocines to 1,2,3,6-tetrahydropyrimidine derivatives

1990 ◽  
Vol 55 (10) ◽  
pp. 2502-2509 ◽  
Author(s):  
Ladislav Štibrányi ◽  
Lubor Fišera ◽  
Rastislav Káčer ◽  
Vladimír Oremus ◽  
Martina Mihulová
Keyword(s):  
Membered Ring ◽  
Dipolar Cycloaddition ◽  
Reaction Sequence ◽  
Pyrimidine Derivatives ◽  
Reaction Conditions ◽  
Photochemical Rearrangement ◽  
Tert Butylamine

An unexpected contraction of the 8-membered ring to a 6-membered one occurring when 6-aryl-7-formyl-2,4,5,8-tetrahydro-1,3-dioxa-5-azocines II were treated with tert-butylamine afforded 4-aryl-5-formyl-1-(1,1-dimethylethyl)-1,2,3,6-tetrahydropyrimidines III. Reaction conditions for the photorearrangement of chlorophenyl-substituted condensed isoxazolines I to II were worked out. The reaction sequence: 1,3-dipolar cycloaddition, photochemical rearrangement, treatment with tert-butylamine constitutes a new route to pyrimidine derivatives from 2H,4H,7H-1,3-dioxepine.

A New Synthesis of l-Hydroxypipecolic Acid

Synlett ◽  
2020 ◽  
Vol 31 (04) ◽  
pp. 355-358 ◽  
Author(s):  
Zhihua Sun ◽  
Zedong Zhang
Keyword(s):  
Synthetic Approach ◽  
Preparative Synthesis ◽  
Reaction Sequence ◽  
New Synthesis

A new synthetic approach toward l-hydroxypipecolic acid is described. This reaction sequence involves eight steps overall, starting from commercially available and inexpensive l-glyceraldehyde acetal. The strategy makes use of readily available reagents and can be used as a preparative synthesis of l-hydroxypipecolic acid. Most of the reaction steps proceed with moderate-to-good yields and do not require any unusual or expensive reagents.

A model study for a novel synthetic approach to 2-carboxyinosines

2000 ◽  
Vol 41 (50) ◽  
pp. 9713-9717 ◽  
Author(s):  
Vasanthakumar Rajappan ◽  
Ramachandra S Hosmane
Keyword(s):  
Synthetic Approach ◽  
Model Study

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%.

scholarly journals A domino reaction for generating β-aryl aldehydes from alkynes by substrate recognition catalysis

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Weiwei Fang ◽  
Felix Bauer ◽  
Yaxi Dong ◽  
Bernhard Breit
Keyword(s):  
Substrate Recognition ◽  
Domino Reaction ◽  
Chemical Transformations ◽  
Reaction Sequence ◽  
Reaction Conditions ◽  
Consecutive Reaction ◽  
Aryl Aldehydes ◽  
Rh Catalyst ◽  
Catalyst Systems ◽  
Step Control

Abstract The development of universal catalyst systems that enable efficient, selective, and straightforward chemical transformations is of immense scientific importance. Here we develop a domino process comprising three consecutive reaction steps based on the strategy of supramolecular substrate recognition. This approach provides valuable β-aryl aldehydes from readily accessible α-alkynoic acids and arenes under mild reaction conditions, employing a supramolecular Rh catalyst containing an acylguanidine-bearing phosphine ligand. Furthermore, the synthesis of a key intermediate of Avitriptan using this protocol is accomplished. The first step of the reaction sequence is proved to be the regioselective hydroformylation of α-alkynoic acids. Remarkably, molecular recognition of the ligand and the substrate via hydrogen bonding plays a key role in this step. Control experiments indicate that the reaction further proceeds via 1,4-addition of an arene nucleophile to the unsaturated aldehyde intermediate and subsequent decarboxylation.

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