نتایج جستجو برای: syntheses

تعداد نتایج: 11788  

Journal: : 2021

The early years of the teaching profession is a period in which teachers both begin and learn how to teach an important career step that affects their way teaching. In this context, there are plenty qualitative quantitative studies conducted different countries international literature on challenges encountered profession's years. This research meta-synthesis study synthesizes results discussin...

Journal: :Physical sciences reviews 2021

Abstract The combination of one-pot methodologies to asymmetric organocatalysis allow a green and direct access many types complex highly functionalized chiral products, including important key intermediates in total syntheses bioactive compounds. A series organocatalysts have already been successfully applied such syntheses. This report collects major developments the synthesis biologically ac...

Journal: :Chemistry 2010
Thomas Magauer Harry J Martin Johann Mulzer

Two convergent total syntheses of the ansa-polyketide (-)-kendomycin (1) are described. The syntheses benefit from the use of readily available and cheap starting materials. Highly complex diastereoselective Claisen-Ireland rearrangements were used to introduce the (E)-double bond and the C16-Me group. The ring closure of the strained ansa macrocycle was achieved by ring-closing metathesis and ...

Journal: :The Journal of organic chemistry 2001
M S Morales-Ríos O R Suárez-Castillo J J Trujillo-Serrato P Joseph-Nathan

A general, efficient, and conceptually new approach to the total syntheses of marine-derived indole alkaloids, including (+/-)-flustramines A (1) and B (2), (+/-)-flustramides A (3) and B (4), and (+/-)-debromoflustramine B (5), is outlined. The key step in the syntheses involves the conjugated addition of an organomagnesium species derived from prenyl bromide to 2-hydroxyindolenines. Compounds...

Journal: :Topics in current chemistry 2012
Uwe Rinner Tomas Hudlicky

This review summarizes recent developments in the total synthesis of morphine alkaloids and some of the semisynthetic derivatives. The literature is covered for the period of 5 years after the publication of the last review in 2005. The syntheses that appeared in this period are covered in detail and are placed in the context of all syntheses of opiate alkaloids since the original one published...

2017
Hang Chu Joel M. Smith Jakob Felding Phil S. Baran

Total syntheses of the complex, highly oxygenated sesquiterpenes thapsigargin (1) and nortrilobolide (2) are presented. Access to analogues of these promising bioactive natural products has been limited to tedious isolation and semisynthetic efforts. Elegant prior total syntheses demonstrated the feasibility of creating these entitites in 36-42 step processes. The currently reported route proce...

Journal: :Nucleic acids research 2004
Archna P Massey Snorri Th Sigurdsson

The chemical syntheses of RNA oligomers containing modifications on the 5'-carbon of the 5'-terminal nucleoside for crystallographic and mechanistic studies of the hairpin ribozyme are reported. Phosphoramidites 4 and 8 were prepared and used in solid phase syntheses of RNA oligomers containing the sequence 5'-N'UCCUCUCC, where N' indicates either 5'-chloro-5'-deoxyguanosine or 5'-amino-5'-deox...

Journal: :The Journal of organic chemistry 2004
James R Vyvyan Celeste Loitz Ryan E Looper Cheryl S Mattingly Emily A Peterson Steven T Staben

Aromatic bisabolene derivatives were prepared by two methods involving cross-coupling of organozinc reagents. The first synthesis of (+/-)-glandulone A (10), as well as syntheses of (+/-)-curcuhydroquinone (8) and (+/-)-curcuquinone (9), were accomplished via coupling of a secondary alkyl zinc reagent (1,5-dimethyl-4-hexenylzinc halide, 18) to protected bromohydroquinones using Pd(dppf)Cl(2) as...

2015
Tze Han Sum Tze Jing Sum Jamie E. Stokes Warren R.J.D. Galloway David R. Spring

Dihydrochalcones and 5-deoxyflavones are types of compounds possessing various biologically interesting properties. Herein, we report the concise and divergent total syntheses of several naturally occurring dihydrochalcones and 5-deoxyflavones from readily available starting materials. The divergent strategy is based around manipulation of a common chalcone scaffold and features application of ...

2012
Antonio Avellaneda Courtney A Hollis Xin He Christopher J Sumby

The syntheses of three new [3]radialenes - hexakis(3,5-dimethylpyrazolyl)-, hexakis(3-cyanophenyl)-, and hexakis(3,4-dicyanophenyl)[3]radialene (1-3) - are reported. Compound 3 is obtained in five steps with an excellent yield of 76% in the key step. Compared to that, the respective steps of the syntheses of 1 and 2 result in lower yields. All compounds adopt a double bladed propeller conformat...

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