ChemInform Abstract: Single-Step Removal of the Allyl Ether Protecting Group with (Ph3P)4RhH and Trifluoroacetic Acid.

ChemInform ◽  
1990 ◽  
Vol 21 (43) ◽  
Author(s):  
F. E. ZIEGLER ◽  
E. G. BROWN ◽  
S. B. SOBOLOV
Keyword(s):  
Trifluoroacetic Acid ◽  
Single Step ◽  
Allyl Ether ◽  
Protecting Group

Synthesis of Structurally Simplified Aureolic Acid Aglycone-C-D-E Trisaccharide Analogues

2002 ◽  
Vol 55 (2) ◽  
pp. 113 ◽  
Author(s):  
W. R. Roush ◽  
N. A. Powell ◽  
R. A. James
Keyword(s):  
Dna Binding ◽  
Complex Formation ◽  
Deoxyribonucleic Acid ◽  
Single Step ◽  
Protecting Group ◽  
Acetate Ester ◽  
Aureolic Acid ◽  
Glycosyl Donors

Syntheses of aureolic acid analogues (5) and (6) with (2S)- and (2R)-acyloin stereochemistry, respectively, are described. The synthesis of (5) utilizes a `C + DE' glycosidation sequence, whereas analogue (6), with unnatural (2R)-acyloin stereochemistry, was synthesized by a sequence in which the entire C-D-E trisaccharide was introduced in a single step. While these syntheses provided sufficient quantities of the two aureolic acid analogues for use in studies of Mg2+ complex formation and deoxyribonucleic acid (DNA) binding, this work also highlights certain limitations in the use of 2-thiophenyl glycosyl donors for synthesis of 2-deoxy-β-glycosides. Specifically, difficulties were encountered in the identification of a protecting group for the aglycone C8 phenol that is fully compatible with the conditions required for reductive removal of the thiophenyl substituents after completion of the glycosidation sequence. Sensitivity of the C2 acyloin stereocentre to the conditions required for deprotection of a phenolic acetate ester are also highlighted in the syntheses of (5), and especially of (6).

Pentamethylbenzyl esters of α-hydroxy acids and their use in depsipeptide synthesis

1968 ◽  
Vol 21 (5) ◽  
pp. 1327 ◽  
Author(s):  
FHC Stewart
Keyword(s):  
Amino Acids ◽  
Trifluoroacetic Acid ◽  
Hydroxy Acid ◽  
Ester Group ◽  
Protecting Group ◽  
Hydroxy Acids ◽  
Acidic Conditions ◽  
Crystalline Nature

Pentamethylbenzyl esters of several a-hydroxy acids have been prepared as possible intermediates in depsipeptide synthesis. Potentially useful features of pentamethylbenzyl as a carboxyl-protecting group are the crystalline nature of the esters, and the rapid cleavage of the group under mild acidic conditions. The glycollate, lactate, and mandelate were coupled with various protected amino acids to form crystalline aminoacyl hydroxy acid derivatives. Selective cleavage of the ester group in these compounds was readily effected with cold trifluoroacetic acid, and the products were used in the synthesis of some representative protected depsipeptides.

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