Tosyl protective group

An alternative strategy is to put a 3-(-2-dioxolanyl)ethanoyl substituent in place first and then add the C7-substituent by a Grignard addition. This approach was applied to the synthesis of 8.2C but in this case it was found necessary to remove the tosyl protecting group prior to cyclization[l]. 

The tosyl protecting group of 4a is removed with sodium naphthalide at -60 °C, and an intramolecular nucleophilic attack of the nitrogen lone pair to the epoxide takes place spontaneously to afford the pyrrolidine hydroxy ester as a labile reaction product, which is immediately protected as the corresponding silyl ether 3a in 68%... 

Compounds with an N-terminal protected azaamino acid residue can be produced by using acylated hydrazines, those with Boc and Z groups being favored. 319 Tosyl-protected compounds can likewise be prepared however, attempts to remove the tosyl protecting group using sodium in liquid ammonia were unsuccessful. 19 ... 

Grignard Reagent pyridinium chlorochromate tosylate protecting group TMS ether Phenols ... 

N-f-butoxycarbonyl group (e.g., 25% HBr-HOAc, TFA-anisole), but is removed by TFA in the presence of dimethyl sulfide within 40-60 minutes at 23°. The N -tosyl protecting group is also removed under these conditions, but at a slower rate. The p-methoxysulfonyl group is also removed by N-hydroxybenzotriazole or by 1 Af NaOH within 1 hour, but only partially by 80% hydrazine hydrate after 24 hours. 

Reduction with sodium/liquid anunonia was introduced 70 years ago for the removal of benzyl-type and tosyl protecting groups and still remains a weU-estabhshed protocol in peptide synthesis.P Benzyl esters are also cleaved with tcrt-butyldimethylsilane in the presence of palladium(II) acetate yielding the corresponding TBDMS esters which are readily hydrolyzed in the presence of ACOH/H2O (see Section 2.2.1.3).P ... 

Paoletti and coworkers used A -tosyl protecting groups to prepare a te-traamine containing only secondary amine functions (Clay et al., 1985). The... 

Radio nucleotide, 6, 13 Radiocerium, 18 Radioimaged, 554 Radioimmunoimaging, 784 Radioimmunotherapy, 18,784 Radioisotopes, 18 Radiolabeled, 784 Radionucleotide, 784 Radiopharmaceutical, 784 Radiostrontium. 18 Removal of tosyl protecting groups by hydrobromic acid, 138, 160 by lithium aluminum hydride, 137, 138, 163... 

Deacetalization. Selectivity of deacetalization has been observed. The method is - rmpatible with acetyl, benzoyl, benzyl, and tosyl protecting groups. 

Cleavage of A-Tosyl Protecting Groups. The deprotection of A-benzenesulfonamides or A-p-toluenesulfonamides of the parent primary or secondary amines occurs in good yield upon heating with excess samarium iodide in a mixture of THF and DMPU (eq 65). The method has also been used in the epimerization-free deprotection of protected a-chiral amines... 

Sulfonamides have also seen great success as partners in the Clauson-Kaas reaction. Similar to amides the pyrroles generated are protected by the starting sulfonamides. Karousis and co-workers reported a successful example of this procedure with 3-formyl-2,5-dimethoxytetrahydrofuran 7 to generate tosyl-protected pyrrole carbaldehyde 8. The tosyl-protecting group was later removed under mildly basic conditions (K2CO3, MeOH at room temperature). 

Thus, treatment of the model ketone 114 with the ylide, generated from 115 under strictly anhydrous conditions, stereoselectively installed the exocyclic double bond (Z/E, 10 1 ratio), leading to the diene 116. After removal of the tosyl protecting group, alkaline hydrolysis followed by macrolactamization of the resulting crude amino acid provided the tricyclic lactam 117. 

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