Anhydrides, mixed s. Carboxylic

Alkoxyformic acid anhydrides, mixed s. Carboxylic alkoxyformic anhydrides Alkoxygermanes... 

Acid anhydrides, mixed s. Carboxylic acid anhydrides, mixed Acid-base catalysis, aromatization by - 26, 946 Acid chlorides... 

Alkoxyformic acid anhydrides, mixed s. Carboxylic alkoxyformic anhydrides Alkoxy groups, position shift 18, 338 suppl. 26 Alkoxyhalides, ring closure 27, 279... 

Anhydrides, mixed s. Borinic carboxylic anhydrides. Carboxylic alkoxyformic -Anhydronucleosides s. Cyclonucleosides Aniline... 

An acyl transfer agent which can be used for the synthesis of acid anhydri s is obtained from the reaction of an acid chloride with 4-benzylpyridine (equation 24). In this way benzoic acid anhydride and cinnamic acid anhydride were obtained in 72% and 57% yields, respectively. As the intermediate, 1-acyl-4-benzylidene-l,4-dihydropyridines, can be isolated, Ais procedure should be well suited for the preparation of mixed anhydrides. Mixed aromatic and aliphatic anh rides can be prepared with 2-ben-zoylthio-l-methylpyridinium chloride and salts of carboxylic acids. These reactions are carried out in aqueous solution. They make use of the high reactivity of esters of thiocarboxylic esters towards nucleophiles. The mixed anhydrides of benzoic acid with 3-phenylpropanoic acid, phenoxyacetic acid, isobu-tyric acid, p-toluic acid and cinnamic acid were formed in 82,79,61,91 and 66% yields, respectively. 

Biological tests show that 3-carboxamide (251), compared with cephalothin, displays equal Staphylococcus activity but is less active against other bacteria (Table XXVII). Other 3-carboxamides were prepared from the 3-carboxylic acid chlorides or mixed anhydrides (U.S. Patent 3,953,436). The 3-nitrone derivative was also used to prepare various five-membered heterocyclic rings at C-3 via 1,3-dipolar cycloaddition reaction with various dipolarophiles. In general, these derivatives showed considerable loss in biological activity (Spry, 1975a,b). 

Tessler, M.M. and Rutenberg, M.W. (1972) Process for Reacting Ungelatinized Starch with a Mixed Carbonic -Carboxylic Anhydride of a Polycarboxylic Acid, U.S. Patent 3,699,095... 

The synthesis of key intermediate 12, in optically active form, commences with the resolution of racemic trans-2,3-epoxybutyric acid (27), a substance readily obtained by epoxidation of crotonic acid (26) (see Scheme 5). Treatment of racemic 27 with enantio-merically pure (S)-(-)-1 -a-napthylethylamine affords a 1 1 mixture of diastereomeric ammonium salts which can be resolved by recrystallization from absolute ethanol. Acidification of the resolved diastereomeric ammonium salts with methanesulfonic acid and extraction furnishes both epoxy acid enantiomers in eantiomerically pure form. Because the optical rotation and absolute configuration of one of the antipodes was known, the identity of enantiomerically pure epoxy acid, (+)-27, with the absolute configuration required for a synthesis of erythronolide B, could be confirmed. Sequential treatment of (+)-27 with ethyl chloroformate, excess sodium boro-hydride, and 2-methoxypropene with a trace of phosphorous oxychloride affords protected intermediate 28 in an overall yield of 76%. The action of ethyl chloroformate on carboxylic acid (+)-27 affords a mixed carbonic anhydride which is subsequently reduced by sodium borohydride to a primary alcohol. Protection of the primary hydroxyl group in the form of a mixed ketal is achieved easily with 2-methoxypropene and a catalytic amount of phosphorous oxychloride. 

S Kim, JL Lee, YC Kim. A simple and mild esterification method for carboxylic acids using the mixed carboxylic-carbonic anhydrides. J Org Chem 50, 560, 1985. 

A ribozyme activity that led to RNA-modifications that are analogous to the 5 -5 pyrophosphate caps of eukaryotic RNA transcripts was selected by Huang and Yarns [84]. Actually the author s intention was to isolate ribozymes which catalyze the formation of a mixed anhydride between an amino acid carboxylate and a 5 -terminal phosphate of an RNA, an activity that is chemically analogous to the activation of amino acids by ATP catalyzed by aminoacyl tRNA synthetases. However, while the selected ribozymes did... 

Unsubstituted thieno[3,4-6]thiophene (3) (see Litvinov and Fraenkel ), was prepared by Cava and Pollack s method for benzo[c]-thiophene i.e., thermal decomposition of H, 3 -benzo[c]thiophene sulfoxide. By refluxing 4/f,6/f-thieno[3,4-ft]thiophene-2-carboxylic acid 5-oxide (91) with acetic anhydride (the synthesis of dihydrothieno-thiophenes will be described below), Wynberg et a/." obtained the mixed anhydride 92 in 95% yield. Hydrolysis gave thieno[3,4-6]-thiophene-2-carboxylic acid (93) (88%). Decarboxylation of the acid (93) gave thienothiophene 3, unstable at room temperature [Eq. (29)]. 

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