Interpretation:
The type of linkage involved in acetonide formation is to be determined and the reason for its susceptibility to acidic hydrolysis and its formation is to be explained.
Concept introduction:
舧 Electrophiles are electron-deficient species, which has positive or partially positive charge. Lewis acids are electrophiles, which accept electron pair.
舧 Nucleophiles are electron-rich species, which has negative or partially negative charge. Lewis bases are nucleophiles, which donate electron pair.
舧 A nucleoside consists of a nucleobase (also termed as nitrogenous base) and a five-carbon sugar (either ribose or deoxyribose).
舧 A
舧 In a nucleoside, the anomeric carbon is linked through a glycosidic bond to the N9 of a purine or N1 of a pyrimidine.
舧 Examples of nucleosides include cytidine, uridine, adenosine, guanosine and thymidine.
舧 Sugar (ribose/deoxyribose) and nitrogenous bases are linked through N-glycosidic bonds.
舧 These glycosidic bonds are formed by condensation reaction of first carbon of sugar molecule with the nitrogen atom
舧 This particular glycosidic bond is stable in basic solutions, but readily hydrolyzes in the presence of acids.
舧 Protection of hydroxyl group at C-2 and C-3 of ribose sugar can be done by treating it with a carbonyl compound. The two alcohol groups behave as
舧 In case the carbonyl involved is acetone, it is called acetonide.
舧 Such groups are stable to bases, but are readily hydrolyzed in mild acids.
舧 The structure of acetonide indicates cyclic diether, in which the alkoxy groups are connected through a single carbon atom and any carbon having two alkoxy groups is said to have involved in acetal formation.
舧 It is susceptible to mild acidic hydrolysis because, in acidic conditions, protons attack the alkoxy oxygen and protonate them. This results in the weakening of the bond of carbon to alkoxy, which readily hydrolyzes.
舧 The acetonide can be formed by the reaction of acetone with a nucleoside in acidic conditions. The proton liberated by the acidic group mediates an electrophilic attack on the carbonyl oxygen, which results in protonation. The protonated product further attacks the nucleoside and produces acetonide.
Want to see the full answer?
Check out a sample textbook solutionChapter 25 Solutions
Organic Chemistry
- (b) Using alanine as an example, draw possible conformations of alanine in a peptide chain and identify which conformer is favoured. (c) Discuss how considering 'allylic strain' [see pages 33-39 of handout 1] can explain the favoured conformation in part b above, and how this is relevant to the B-sheet conformation in peptides/proteins.arrow_forwardgive detailed solution with explanation neededarrow_forward5. The purpose of SDS in SDS-PAGE is (a) to selectively bind the target protein. (b) to maintain buffer pH in the gel. (c) to cause separation to be on the basis of molecular weight only. (d) to initiate polymerization of acrylamide to form a gel. (e) none of the above.arrow_forward
- Classify the molecules in Problems 26.43 and 26.48 as either carbon-chain or heterochain polymers. Identify the repeating unit in each polymer and draw the condensed formulaarrow_forwardThe anticlotting property of heparin is partly the result of the negative charges it carries. ( Q.) Identify the functional groups that provide the negative charges.arrow_forward(a) An aliphatic aminoglycoside is relatively stable to base, but it is quickly hydrolyzed bydilute acid. Propose a mechanism for the acid-catalyzed hydrolysis.NHHCH2RR2NH2 + sugarRHHOH OHOH Oan aliphatic ribosideH3O+ +(b) Ribonucleosides are not so easily hydrolyzed, requiring relatively strong acid.Using your mechanism for part (a), show why cytidine and adenosine (for example)are not so readily hydrolyzed. Explain why this stability is important for livingorganisms.arrow_forward
- Treatment of a new protein with dansyl chloride reveals two (2) dansyl-labelled derivatives of amino acids, alanine and methionine. What can you deduce about the structure of the proteinfrom these results?arrow_forwardUsing the information in Tables 25.1 and 25.2, determine which form of the amino acid below meets the criteria below. Enter the answer using parentheses, e.g. (H). но. но. HO. NH3 NH3 NH3 (A) (B) (C) NH3 NH2 (D) (E) Dominates at pH 1 Use parentheses! Does not dominate at any pH Use parentheses!arrow_forwardA tripeptide contains lysine (R= -(CH₂)4NH₂), phenylalanine (R= -CH₂C6H5) and glycine (R= -H). It was found that the tripeptide reacts with 2 moles of DNFB to give compound A. When compound A was treated with SOCI2, glycine was activated. When hydrolyzed, both NH₂ groups of lysine were found to be DNP-labelled. What is the structure of the tripeptide? Select one: H (CH₂)2NH2 CH NH CH H₂N O O H₂N H₂N H₂N C (CH2)4NH2 CH 010 (CH2)4NH2 CH C=O CH,Ph CH NH NH NH CH CH,Ph CH H 010 CH CH,Ph CH (CH2)4NH2 ΝΗ NH NH NH CH,Ph CH H CH COOH H CH COOH COOH COOHarrow_forward
- 26. (i) Why is the ester formation of alcohols and acid chlorides done in a weakly basic solution like pyrmidine? (ii) Why is this setup not viable for alcohols and carboxylic acids to form esters? pyrimidine deprotonates the alcohol; the alkoxide ion forms pyrimidine deprotonates the alcohol; the carboxylate ion forms pyrimidine deprotonates the tetrahedral intermediate; the alkoxide ion forms pyrimidine deprotonates the tetrahedral intermediate; the carboxylate ion formsarrow_forward(i) Why do actinoids show wide range of oxidation states? (ii) Why is actinoid contraction greater than lanthanoid contraction?arrow_forwardWhat is the Answer for (a.) ?arrow_forward
- Chemistry for Today: General, Organic, and Bioche...ChemistryISBN:9781305960060Author:Spencer L. Seager, Michael R. Slabaugh, Maren S. HansenPublisher:Cengage LearningOrganic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning