Propanoyl group

This chiral auxiliary has been applied to the enantioselective synthesis of a-alkyl carboxylic acids such as (5 )-2-methyl-4-pentenoic acid. A retrosynthetic analysis of the carbon skeleton of 2-methyl-4-pentenoic acid suggests preparation by alkylation of the enolate of a propanoyl group with an allyl halide. 

As actually carried out, the chiral auxiliary was acylated at nitrogen with propanoyl chloride and the propanoyl group then deprotonated at its a carbon with lithium diiso-propylamide forming an enolate. 

Iwata T., Azuma J., Okamura K., Muramoto M., Chun B., Preparation and NMR assignments of cellulose mixed esters regioselectively substituted by acetyl and propanoyl groups, Carbohyd. Res., 224, 1992,277-283. 

To prepare A-propanoyl-, A-hexanoyl-, and A,0-quatemary substituted chitosan sulfate with the similar structure of heparin, the chemical modification of chitosan sulfate was carried out by Huang et al. (2003). The propanoyl (SCOS II) and hexanoyl (SCOS III) groups increased the thromboplastin time (APTT) activity, and the propanoyl groups also increased the thrombin time (TT) anticoagulant activity slightly, while the A,0-quaternary chitosan sulfate (SCOS IV) showed only a slight TT coagulant activity. 

FIGURE 12 8 Electrostatic potential map of propanoyl cation [(CH3CH2C=0) ] The region of greatest positive charge is associated with the carbon of the C=0 group... 

Trichloromethyl chloroformate has proven effective in the preparation of N-carboxy-a-amino acid anhydrides from amino acids, and various compounds having isocyanate, acid chloride, and chloroformate groups.For example, trichloromethyl chloroformate may be used instead of phosgene in the preparation of 2-tert-butoxycarbonyloxyimino-2-phenylacetonitrile. The use of this reagent is illustrated here by the synthesis of 3-isocyanato-propanoyl chloride from 3-aminopropanoic acid hydrochloride. 

A new method for the synthesis of 2-substituted, as well as 2,4- and 2,5-disubstituted, cyclopentanones in 53-93% yield has been reported.81 For example, the Lewis acid catalyzed transformation of l-propanoyl-l-(4-tolylsulfanyl)cyclobutane gave 2-ethyl-2-(4-tolylsulf-anyl)cyclopentanone (1) in 93 % yield. The formation of the cyclopentanone is best explained by a mechanism which involves initial coordination of aluminum trichloride to the carbonyl oxygen, followed by ring expansion to form the sulfur-stabilized carbocation. Finally, migration of the ethyl group to the carbocation center regenerates concomitantly the carbonyl function.81... 

The SARs of the taxoids 28 and 29 against MCF7-R show that the bulkiness of the C-10 substitution exhibits considerable effects on cytotoxicity. It appears that the propanoyl and cyclopropanecarbonyl groups are optimal as demonstrated by the exceptionally high potency of 28a (SB-T-1213), 28b (SB-T-1214), and 29a. As the size of the C-10 modifier increases, the activity shows a fairly steady decline as exemplified by the comparison of 10-dimethylcarbamoyl taxoid 28c (IC50 = 4.9... 

All of the protons in the structures in part b are equivalent and appear as a sharp, single peak. One way to test whether protons are equivalent is to replace any one of them by some group X. If the same product is obtained regardless of which proton is replaced, then the protons must be equivalent. Try this test with the compounds in parts a and c. Note that diethyl ether (part a) and propanoyl chloride (part c), has two sets of equivalent protons (CH2 and CH3). 

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