Steroids aliphatic carboxylic acids

It has been shown that the spiro-j5-epoxide (181) can be converted into the spiro-y-lactone (182) by reaction with dimetalated acetic acid formed under mild conditions by treating acetic acid with lithium di-isopropylamide. Extension to homologous and functionally substituted examples has established that the dimetalation of aliphatic carboxylic acids is a general phenomenon which makes it possible to prepare a large array of steroidal spiro-y-lactones. ... 

Unhindered aliphatic carboxylic acids such as those found in steroidal side-chains can be degraded by three carbons by a four-step procedure (Scheme 11), via dihydro-oxazole formation, dehydrogenation, and ozonolysis,which should be applicable to a good range of (saturated) substrates. 

Ammonium hexanitratocerate(IV) is an efficient catalyst for fast esterification of carboxylic acids and alcohols under mild conditions (Goswami and Chowdhury, 2000). The reaction can be carried out under solventless conditions, or in chloroform. The reaction works with primary and secondary alcohols, and with aliphatic carboxylic acids. No reaction was observed for tertiary alcohols or for aromatic acids. The method is of interest because it is also applicable to the esterification of alcohols based on steroids and on other natural products (scheme 37). Pan and coworkers described the esterification of phenylacetic acids and cis-o cic acid with simple primary and secondary alcohols in presence of an excess of CAN at room temperature (Pan et al., 2003). The alcohol acted as solvent. Ammonium hexanitratocerate(IV) does catalyze not only the esterification of carboxylic acid, but also the transesterification with another alcohol (Stefane et al., 2002). 

Derivatized compounds with fluorophores (amino acids, steroids, aliphatic amines, carboxylic acids, catecholamines, etc.)... 

The exchange of protons a to a carboxylic acid salt (R—CH2—COOR -> R—CD2 COOR ) is known to proceed satisfactorily with various aliphatic and aromatic acid salts under strongly alkaline conditions.7,43 This reaction is presumably applicable to steroid derivatives (e.g. bile acids) as well, but examples are lacking in this field. 

The Favorski rearrangement is widely applicable. In the aliphatic series it leads to branched-chain carboxylic acids and in the cycloalkane series to ring contraction. The latter feature has been made use of in conversion of a six-membered into a five-membered steroid ring d and in the synthesis of cubane. 

Some mammalian organs, particularly the liver and kidney, have the ability to convert numerous aliphatic or aromatic alcohols and carboxylic acids into their respective /3-D-glucosiduronic acids these can be transported in the blood or excreted through the urine or bile. This reaction pertains not only to such foreign substances as drugs, but also to such important endogenous compounds as steroid hormones, thyroxine, or bilirubin. 

Nickel peroxide, which is readily obtainable, has proved to be a useful oxidation agent Permanganate oxidation is an effective general method for the conversion of aliphatic nitro into oxo compounds a,/3-Ethyleneketones as well as 1,4-naphthoquinones can be cheaply and safely epoxidized with hypochlorite A rapid direct preparation of peroxy acids in methanesulfonic acid has been published An efficient method for the oxidative removal of the methyl group in position 19 of steroids has been described The application of hydride transfer for carboxylations has been continued. 

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