Azetidinone antibiotics. 19. A simple method for the removal of p-nitrobenzyl acid-protective group

Lammert, S. R.; ELLIS, A. I.; Chauvette, Robert R.; Kukolja, Stjepan

doi:10.1021/jo00400a048

Cited by 28 publications

(4 citation statements)

References 2 publications

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“…It is highly resistant to acids and removed using a variety of reducing agents such as Na 2 S, Na 2 S 2 O 4 , or SnCl 2 or by catalytic hydrogenation. − Solid-phase removal is performed by treatment with 8 M SnCl 2 in DMF containing 1.6 mM AcOH and 0.2% phenol for 5 h at 25 °C or three treatments of 30 min at 60 °C . Washings with DMF, MeOH, and DMF, treatment with 8 M benzenesulfinic acid in DMF for 30 min at 25 °C, and further washings with DMF and MeOH are performed to eliminate the quinonimine methide formed during the removal .…”

Section: α-Carboxylic Acidmentioning

confidence: 99%

Amino Acid-Protecting Groups

2009

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Section: α-Carboxylic Acidmentioning

confidence: 99%

Amino Acid-Protecting Groups

2009

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“…These esters are stable to the acid conditions used to remove the Boc group, as well as the small number of cycles of piperidine/DMF used to remove the Fmoc group 128, 129. The esters can be cleaved by reducing agents, such as Zn in HOAc, Na 2 S, Na 2 S 2 O 4 , or SnCl 2 in aqueous organic solvents 128, 130, 131. For the use of p NB in the solid phase, SnCl 2 is a very convenient reagent because when dissolved in DMF, a common solvent used in SPPS, the nitro group is easily reduced.…”

Section: C‐terminal Carboxyl Protecting Groupsmentioning

confidence: 99%

Orthogonal protecting groups forNα-amino andC-terminal carboxyl functions in solid-phase peptide synthesis

Alberício¹

2000

Biopolymers

108

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For the controlled synthesis of even the simplest dipeptide, the Nα‐amino group of one of the amino acids and the C‐terminal carboxyl group of the other should both be blocked with suitable protecting groups. Formation of the desired amide bond can now occur upon activation of the free carboxyl group. After coupling, peptide synthesis can be continued by removal of either of the two protecting groups and coupling with the free C‐terminus or Nα‐amino group of another protected amino acid. When three functional amino acids are present in the sequence, the side chain of these residues also has to be protected. It is important that there is a high degree of compatibility between the different types of protecting groups such that one type may be removed selectively in the presence of the others. At the end of the synthesis, the protecting groups must be removed to give the desired peptide. Thus, it is clear that the protection scheme adopted is of the utmost importance and makes the difference between success and failure in a given synthesis. Since R. B. Merrifield introduced the solid‐phase strategy for the synthesis of peptides, this prerequisite has been readily accepted. This strategy is usually carried out using two main protection schemes: the tert‐butoxycarbonyl/benzyl and the 9‐flourenylmethoxycarbonyl/tert‐butyl methods. However, for the solid‐phase preparation of complex or fragile peptides, as well as for the construction of libraries of peptides or small molecules using a combinatorial approach, a range of other protecting groups is also needed. This review summarizes other protecting groups for both the Nα‐amino and C‐terminal carboxyl functions. © 2000 John Wiley & Sons, Inc. Biopoly 55: 123–139, 2000

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“…It is noteworthy that esters which are cleavable under very different conditions are tolerated (i.e. methyl, benzyl, and p-nitrobenzoyl [16] variants) as are both Boc and Cbz protection of the amino functionality. Larger protecting groups bring about very high levels of diastereocontrol.…”

Section: C)mentioning

confidence: 99%

A Practical Aryl Unit for Azlactone Dynamic Kinetic Resolution: Orthogonally Protected Products and A Ligation‐Inspired Coupling Process

2014

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The first strategy for bringing about enantioselective azlactone dynamic kinetic resolution to generate orthogonally protected amino acids has been developed. In the presence of a C2-symmetric squaramide-based catalyst, benzyl alcohol reacts with novel yet readily prepared tetrachloroisopropoxycarbonyl-substituted azlactones to generate trapped phthalimide products of significant synthetic interest with excellent enantiocontrol. These materials are masked amino acids which are demonstrably orthogonally protected: cleavage of the phthalimide can be achieved in the presence of the ester and vice versa. This process could be utilized to bring about a highly stereoselective ligation-type coupling of protected serines (at stoichiometric loadings) with racemic azlactones derived from both natural and abiotic amino acids. After deprotection, a subsequent base-mediated O→N acyl transfer occurs to form a dipeptide.

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Azetidinone antibiotics. 19. A simple method for the removal of p-nitrobenzyl acid-protective group

Cited by 28 publications

References 2 publications

Amino Acid-Protecting Groups

Amino Acid-Protecting Groups

Orthogonal protecting groups forNα-amino andC-terminal carboxyl functions in solid-phase peptide synthesis

A Practical Aryl Unit for Azlactone Dynamic Kinetic Resolution: Orthogonally Protected Products and A Ligation‐Inspired Coupling Process

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