Degradation, Barbier-Wieland oxidative

This procedure, coupled with the procedure described on p. 41, illustrates the Barbier-Wieland method for systematically degrading carboxylic acids. foxwor-Desoxycholic acid may be prepared from wor-desoxycholic acid by repetition of this procedure. If the chromic acid oxidation product is not sufficiently solid to filter after dilution with water, the mixture must be extracted with ether and washed with dilute hydrochloric acid before the alkaline extraction. Wxwor-Desoxycholic acid may be crystallized from ethyl alcohol. It melts at 239-241°. 

MIESCHER DEGRADATION. Adaptation of the Barbier-Wieland carboxylic acid degradation to pcrmil simultaneous elimination of three carbon atoms, as in degradation of the bile acid side chain to the methyl ketone stage. Conversion of the methyl ester of the bile acid to the tertiary alcohol, followed by dehydration, bromination. dehydrohalogenatinn, and oxidation of the diene yields die required degraded ketone. 

Synthesis from Steroidal and Alkaloidal Intermediates Steroidal intermediates have been employed in the synthesis of certain alkaloids such as dihydroconessine (58)(ref.55), one of the 3-aminoconanine bases, from the bile acid compound 3-B-acetoxybisnorcholenic acid, a substance obtained from appropriately-protected coprostanol by oxidation and two Barbier-Wieland degradations. The method consisted in converting the carboxyl into a formylamino group, the acetoxy into a tosylate which was then substituted by a dimethylamino group, reduction of the formylamino to methylamino and formation of the five-membered ring E by... 

Barbier-Wieland degradation. Stepwise carboxylic acid degradation of aliphatic acids (particularly in sterol side chains) to the next lower homo log. The ester is converted to a tertiary alcohol that is dehydrated with acetic anhydride, and the olefin oxidized with chromic acid to a lower homologous carboxylic acid. 

A fairly straightforward scheme, called the Barbier-Wieland degradation, was at that time used for determining the number of carbon atoms in an ahphatic acid fragment. This involves first converting the carboxylic acid 11-1 to the corresponding ester 11-2 (Scheme 1.11). Reaction of the ester with phenylmagnesium bromide leads to carbinol 11-3. Treatment with acid leads to dehydration and formation of the olefin 11-4. Oxidation by one of several methods cleaves... 

A synthesis of rac-famesiferol-C, rac-33, is presented in Scheme 6. Baeyer-Villiger oxidation of ketone 44 resulted in the formation of the 7-oxabicyclo[2.2.1]heptane 46, not in the expected hydroxyl lactone 45. Standard Barbier-Wieland degradation of 46 (CH2N2, then PhMgBr followed by acidic... 

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