Esters Reactivity Chart

Thiol esters, which are more reactive to nucleophiles than are the corresponding oxygen esters, have been prepared to activate carboxyl groups for both lactoniza-tion and peptide bond formation. For lactonization S-f-butyl and S-2-pyridyP esters are widely used. Some methods used to prepare thiol esters are shown below. The S-r-butyl ester is included in Reactivity Chart 6. 

Reactivity Chart 2. Protection for the Hydroxyl Group Esters... 

Polymer-supported esters are widely used in solid-phase peptide synthesis, and extensive information on this specialized protection is reported annually. Some activated esters that have been used as macrolide precursors and some that have been used in peptide synthesis are also described in this chapter the many activated esters that are used in peptide synthesis are discussed elsewhere. A useful list, with references, of many protected amino acids (e.g., -NH2, COOH, and side-chain-protected compounds) has been compiled/ Some general methods for the preparation of esters are provided at the beginning of this chapter conditions that are unique to a protective group are described with that group/ Some esters that have been used as protective groups are included in Reactivity Chart 6. 

Two new sections on the protection of phosphates and the alkyne-CH are included. All other sections of the book have been expanded, some more than others. The section on the protection of alcohols has increased substantially, reflecting the trend of the nineties to synthesize acetate- and propionate-derived natural products. An effort was made to include many more enzymatic methods of protection and deprotection. Most of these are associated with the protection of alcohols as esters and the protection of carboxylic acids. Here we have not attempted to be exhaustive, but hopefully, a sufficient number of cases are provided that illustrate the true power of this technology, so that the reader will examine some of the excellent monographs and review articles cited in the references. The Reactivity Charts in Chapter 10 are identical to those in the first edition. The chart number appears beside the name of each protective group when it is first introduced. No attempt was made to update these Charts, not only because of the sheer magnitude of the task, but because it is nearly impossible in... 

Carboxylic acids, protection of, 224-276 as amides and hydrazides, 270-276 as esters, 227-270 Reactivity Chart 6, 433-436 S-Carboxymethyl thioethers, to protect thiophenols, 294-295 Catechols, protection of, 170-174 as cyclic acetals and ketals, 170-172 as cyclic esters, 173-174 Reactivity Chart 4, 425-428 CBZ, see Benzyl carbamates Chloroacetamides, to protect amines, 352-353... 

Hydroxyl group, protection of, 10-142 as esters, 87-118 Reactivity Chart 2, 417-420 as ethers, 14-87 ... 

Phenacyl ethers, to protect phenols, 153 Phenacylsulfonamides, to prote ct amines, 385 Phenols, protection of, 143-170 as esters, 162-170 as ethers, 145-162 Reactivity Chart 4, 425-428 Phenothiazinyl-(10)-carbonyl derivatives, to protect amines, 346... 

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