Anhydrides, intramolecular

Sulfates 2-Carb-25. N-Substitution 2-Carb-26. Intramolecular anhydrides 2-Carb-27. Intermolecular anhydrides 2-Carb-28. Cyclic acetals... 

A/-Acetyl-4,8,9-tri-0-acetyl-a-neuraminic acid (ot-Neu4,5,8,9Ac4) 2-Carb-26. Intramolecular anhydrides... 

An intramolecular ether (commonly called an intramolecular anhydride), formally arising by elimination of water from two hydroxy groups of a single molecule of a monosaccharide (aldose or ketose) or monosaccharide derivative, is named by attaching the (detachable) prefix anhydro- preceded by a pair of locants identifying the two hydroxy groups involved. 

Cyclization of Anhydrides. Instead of the acid chloride, an intramolecular anhydride of the type LXXIX may be used for cyclization by the Friedel-Crafts reaction (Table VII, examples marked by h ). This resembles the intermolecular acylation with succinic anhydride, and a similar procedure is generally followed. The product of ring closure is a keto acid LXXX. Nitrobenzene 9i 6,1120 is a generally effective solvent for the reaction sym-tetrachloroethane also may be used.121... 

First prepared by C. F. Gerhardt from benzoyl chloride and carefully dried potassium acetate (1), acetic anhydride is a symmetrical intermolecular anhydride of acetic acid die intramolecular anhydride is ketene [463-51 4-]. Benzoic acetic anhydride [2819-08-1] undergoes exchange upon distillation to yield benzoic anhydride [93-97-0] and acetic anhydride. 

Reaction (10.23) (R = Me, Bu, MejCHCH, or Ph) may be catalysed by 7V,A/-dialkyl-carboxamides, such as dmf, at between 40 and 150 C [388]. Using iron(III) catalysts, such as iron(IIl) chloride, in a sealed tube, the intramolecular anhydrides were efficiently converted into their acid chlorides [278a] ... 

Even though dendrimer surfaces can be constructed to exhibit all possible functionalities, amine-terminating groups are synthetically more appealing and have been used most extensively. The potentially useful thiolated dendrimers self-oxidize, while carboxylated dendrimers tend to form intramolecular anhydrides once activated. This last situation may cause defects upon carbohydrate attachment. Although alcohols seem also attractive, a priori, their direct use in glycosylation chemistry is hampered by potentially difficult complete anomeric stereocontrol. 

Intramolecular anhydride/peranhydride exchange through in situ formation of a peroxy p-nitrophenyl anhydride intermediate has been inferred to form diphenoyl peroxide, as evidenced by its chemiluminescent decomposition (Scheme 21) <86JOC2050>. 

An interesting and novel transformation was observed during the attempted fluorination of D-l,2-0-isopropylidene-3,4,5-tri-0-benzyl-myo-inositol using diethylaminosulfur trifluoride (DAST). The bicyclic anhydro-inositol 157 was isolated in 94% yield, presumably the result of fluoride-induced debenzylative intramolecular anhydride formation as depicted in Scheme 25. ... 

During reaction of these blocking agents an acidic function (3-nitro-benzoyl-2-carbox-ylate or benzoyl-2-sulfonate) from the intramolecular anhydride bond is Uberated in its salt form. All blocked defective sequences therefore additionally are marked by this acidic moiety. They can be separated from the end product by ion exchange chromatography, since the acidity of the marker function is much more pronounced than any peptide car-boxylate on terminal or side [168] positions (Fig. 51). Though acetylation likewise suppresses the formation of failure sequences, it effects no facilitated separability of synthetic peptide by-products. 

Problem 5.10. Of the two isomeric (maleic and fumaric) butenedioic acids (H02CCH=CHC02H), only one of them (maleic acid) forms an intramolecular anhydride. Draw and label the structures of the two acids and the one anhydride. 

Carbonyl Insertions. DSC has been used as a replacement for Phosgene in the cyclization of AT-aralkyl a-amino acids to Af-carboxyanhydrides (eq 6). This method releases N-hydroxysuccinimide as a byproduct, which is only weakly acidic and so does not affect any acid sensitive groups, whereas phosgene releases 2 equiv of hydrogen chloride. Unlike in ester formation using carboxylates, where the central carbonyl group of DSC is released as CO2, with better nucleophiles, such as secondary a-amino functions, incorporation of the carbonyl group occurs. This is assumed to be by A -substitution by R-CO-, followed by intramolecular anhydride formation by tertiary amine. Similar carbonyl insertions by N,N -Carbonyldiimidazole (CDI)... 

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