scholarly journals Effect of uridine protecting groups on the diastereoselectivity of uridine-derived aldehyde 5’-alkynylation

2017 ◽  
Vol 13 ◽  
pp. 1533-1541 ◽  
Author(s):  
Raja Ben Othman ◽  
Mickaël J Fer ◽  
Laurent Le Corre ◽  
Sandrine Calvet-Vitale ◽  
Christine Gravier-Pelletier
Keyword(s):  
Carbonyl Group ◽  
Protecting Groups ◽  
Grignard Reagents ◽  
Group Effect ◽  
Protecting Group ◽  
Alkyl Groups ◽  
Silyl Groups

The 5’-alkynylation of uridine-derived aldehydes is described. The addition of alkynyl Grignard reagents on the carbonyl group is significantly influenced by the 2’,3’-di-O-protecting groups (R1): O-alkyl groups led to modest diastereoselectivities (65:35) in favor of the 5’R-isomer, whereas O-silyl groups promoted higher diastereoselectivities (up to 99:1) in favor of the 5’S-isomer. A study related to this protecting group effect on the diastereoselectivity is reported.

Alkyl 1-[2-(oxido anion)-, 3-, 4-, 5-alkyl substituted]phenyl ketyl radicals

1979 ◽  
Vol 44 (6) ◽  
pp. 1731-1741 ◽  
Author(s):  
Andrej Staško ◽  
Ľubomír Malík ◽  
Alexander Tkáč ◽  
Vladimír Adamčík ◽  
Eva Maťašová
Keyword(s):  
Electron Donor ◽  
Unpaired Electron ◽  
Grignard Reagents ◽  
Slight Effect ◽  
Benzene Nucleus ◽  
Alkyl Groups ◽  
Splitting Constant

Reactions of R2,R3-alkyl substituted 2-hydroxybenzenecarboxylic acids 2-HO-C6H2R2-COOH with Grignard reagents R1MgBr in the presence of nickel give stable aryl alkyl ketyl radicals 2-O--R2-, R3-C6H2-CO--R1 where R1 = CH3, C2H5, C2D5, n-C3H7 and R2,R3 = CH3, C2H5, i-C3H7, t-C4H9. The β protons of ketyl group are equivalent (splitting constant 1.25 mT) and non-equivalent (splitting constants within 0.5 to 1.5 mT) for R1 = methyl and other alkyl groups, respectively. Interaction of the γ protons with the unpaired electron was only observed in the case of R1 = n-propyl (splitting constants about 0.07 mT). The substituents R1 have but slight effect on values of splitting constants of the protons in R2,R3 and vice versa. Also splitting constants of the benzene nucleus (a4H = 0.55 mT, a6H = 0.44 mT) are only slightly affected by the substituents R1,R2,R3, which indicates dominant electron-donor effect of the oxido-anion group eliminating the relatively smaller contributions of the alkyl substituents.

Stereocontrolled Synthesis of Heterocyclic C-Nucleosides. Protecting Group Effect and Molecular Modeling Studies

2002 ◽  
Vol 67 (11) ◽  
pp. 3724-3732 ◽  
Author(s):  
Dominique Guianvarc'h ◽  
Jean-Louis Fourrey ◽  
Marie-Elise Tran Huu Dau ◽  
Vincent Guérineau ◽  
Rachid Benhida
Keyword(s):  
Molecular Modeling ◽  
Group Effect ◽  
Protecting Group ◽  
Modeling Studies ◽  
Stereocontrolled Synthesis ◽  
Molecular Modeling Studies

STRUCTURAL AND SOLVENT EFFECTS ON THE n → π*(′U ← ′A) TRANSITIONS IN ALIPHATIC CARBONYL DERIVATIVES: EVIDENCE FOR HYPERCONJUGATION IN THE ELECTRONICALLY EXCITED STATES OF MOLECULES

1960 ◽  
Vol 38 (12) ◽  
pp. 2508-2513 ◽  
Author(s):  
C. N. R. Rao ◽  
G. K. Goldman ◽  
A. Balasubramanian
Keyword(s):  
Hydrogen Bonding ◽  
Carbonyl Group ◽  
Excited States ◽  
Solvent Effects ◽  
Electronically Excited States ◽  
Carbonyl Derivatives ◽  
Alkyl Groups ◽  
Electronically Excited

The n → π* transition of the carbonyl group has been studied in solvents of varying degree of polarity and hydrogen-bonding ability, in a number of aliphatic carbonyl derivatives. Evidence for hyperconjugation of the alkyl groups in the electronically excited states of molecules has been presented.

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.

Protecting-group-free synthesis of haterumadienone- and puupehenone-type marine natural products

2017 ◽  
Vol 19 (9) ◽  
pp. 2140-2144 ◽  
Author(s):  
Hong-Shuang Wang ◽  
Hui-Jing Li ◽  
Jun-Li Wang ◽  
Yan-Chao Wu
Keyword(s):  
Natural Products ◽  
Transition Metals ◽  
Marine Natural Products ◽  
Protecting Groups ◽  
Protecting Group

The atom- and step-economical synthesis of seven puupehenone- and haterumadienone-type marine natural products without the use of protecting groups and transition metals has been achieved from the abundant feedstock chemical sclareolide in only 6 to 9 steps.

Chemistry of glucal halohydrins(II): An unusual protecting group effect in the competitive formation of formyl furanosides and methyl glycosides

1997 ◽  
Vol 300 (4) ◽  
pp. 301-313 ◽  
Author(s):  
John S. Kozlowski ◽  
Cecilia H. Marzabadi ◽  
Nigam P. Rath ◽  
Christopher D. Spilling
Keyword(s):  
Group Effect ◽  
Protecting Group

Protecting-Group-Directed Regio- and Stereoselective Oxymercuration–Demercuration: Synthesis of Piperidine Alkaloids Containing 1,2- and 1,3-Amino Alcohol Units

Synthesis ◽  
2017 ◽  
Vol 50 (05) ◽  
pp. 1113-1122 ◽  
Author(s):  
Santosh Tilve ◽  
Sandesh Bugde ◽  
Prajesh S.Volvoikar
Keyword(s):  
Amino Alcohol ◽  
Protecting Groups ◽  
Protecting Group ◽  
Efficient Synthesis ◽  
Piperidine Alkaloids ◽  
Naturally Occurring ◽  
Pipecolinic Acid

An efficient synthesis of naturally occurring 1,2- and 1,3-amino alcohol unit containing 2-substituted piperidine alkaloids and their analogues has been developed from l-pipecolinic acid. The protocol describes the regio- and stereoselective oxymercuration–demercuration of 2-alkenyl piperidines based on protecting groups to give piperidine alkaloids as a key step.

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