Transcription of PROTECTING GROUPS 57 Smith: Chapter 7
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PROTECTING GROUPS 57 Smith: Chapter 7
PROTECTING GROUPS 57 Carey & Sundberg Chapter # 1; 2; 3a, b, c ;Smith: Chapter 7 PROTECTING Greene & Wuts, Protective GROUPS in Organic Synthesis (2nd edition) J. Wiley & Sons, J. Kocienski, PROTECTING GROUPS , Georg Thieme Verlag, groups2 Ketones and Acids- Protect functional GROUPS which may be incompatible with a set of reactionconditions- 2 step process- must be efficient- Selectivity a. selective protectionb. selective deprotectionHydroxyl PROTECTING GroupsEthersMethyl ethersR-OH R-OMedifficult to remove except for on phenolsFormation:- CH2N2, silica or HBF4- NaH, MeI, THFC leavage:- AlBr3, EtSH- PhSe -- Ph2P -- Me3 SiIOOOBzOMeOOOBzOHAlBr3, EtSHTL 1987, 28 , 3659 Methoxymethyl ether MOMR-OH R-OCH2 OMestable to base and mild acidFormation:- MeOCH2Cl, NaH, THF- MeOCH2Cl, CH2Cl2, iPr2 EtNCleavage- Me2 BBr2TL 1983, 24 , 3969 PROTECTING GROUPS 58 Methoxyethoxymethyl ethers (MEM)R-OH R-OCH2 OCH2CH2 OMestable to base and mild acidFormation:- MeOCH2CH2 OCH2Cl, NaH, THF- MeOCH2CH2 OCH2Cl, CH2Cl2, iPr2 EtNTL 1976, 809 Cleavage- Lewis acids such as ZnBr2.
PROTECTING GROUPS 58 Methoxyethoxymethyl ethers (MEM) R-OH → R-OCH2OCH2CH2OMe stable to base and mild acid Formation: - MeOCH2CH2OCH2Cl, NaH, THF - MeOCH2CH2OCH2Cl, CH2Cl2, iPr2EtN TL 1976, 809 Cleavage - Lewis acids such as ZnBr2, TiCl4, Me2BBr2 C 5 H 11 O MEM-O
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Protecting Groups, Acid, Amino Groups, Amino, Coupling Reagents, Amino acid, Amino protecting groups, ORTHOGONALITY OF PROTECTING GROUPS, Protecting, Groups, Solid Phase Peptide Synthesis, Strategies and Resins, Review of Organosilanes in Organic Chemistry, Methods in Peptide Synthesis. Part, Amino Acid-Protecting Groups, Protecting Groups Handout A