Carboxylic acid derivatives synthesis Subject

For a complete description of the synthetic utility of the Houben-Hoesch reaction as it applies to other aromatic systems, as well as some mechanistic discussions, the reader is directed to two reviews on the subject. Due to the diminished electrophilic reactivity of nitriles compared to other carboxylic acid derivatives as well as the broad number of Friedel-Crafts substrates, most Houben-Hoesch pyrrole acylation reactions are conducted intramolecularly. However, an impressive intermolecular example was delineated by Chang and co-workers in efforts directed toward the synthesis of novel 2-[5-aroylpyrrolo]alkanoic acids, for evaluation of their potential analgesic and anti-inflammatory activities. Treatment of substituted pyrrole 4 and 3-cyanopyridine (5) with acid in dry chloroform resulted in the preparation of 6 in good yield. 

Synthesis of 210 was started from preparation of chiral diamine 211 (Scheme 50) [172], In particular, D-serine methyl ester was converted to iV-benzyl derivative 212, which was transformed into carboxylic acid 212 using reaction with chloroacetyl chloride and subsequent hydrolysis. Carboxylic acid 212 was subjected to coupling with benzyl amine, reduction, reaction with ethyl oxalyl chloride and reductive cyclization to give bicyclic compound 213. Finally, 211 Two-step reduction of 213 led to the formation of diamine 211, which was isolated as dihydrochloride. Reaction of 211 with dichloro derivative 215 and then - hydrazine hydrate gave the product 216, which was coupled with carboxylic acid 217 and subjected to catalytic hydrogenation to give 210. 

Synthesis of optically active PF-04634817 (271) based on commercially available (-)-Vince Lactam as chirality source. Starting from (-)-Vince Lactam the chiral key 4-amino-2-cyclopentene-l-carboxylic acid derivative 286 was synthesized. The componnd 286 is dimethyl pyrrole protected form of corresponding aminoacid, which was subjected to amide coupling with Boc-protected diamine 287 to give... 

In the early 1930 s, when the prime research aim was the commercial synthesis of the sex hormones (whose structures had just been elucidated), the principal raw material available was cholesterol extracted from the spinal cord or brain of cattle or from sheep wool grease. This sterol (as its 3-acetate 5,6-dibromide) was subjected to a rather drastic chromic acid oxidation, which produced a variety of acidic, ketonic and hydroxylated products derived mainly by attack on the alkyl side-chain. The principal ketonic material, 3j -hydroxyandrost-5-en-17-one, was obtained in yields of only about 7% another useful ketone, 3 -hydroxypregn-5-en-20-one (pregnenolone) was obtained in much lower yield. The chief acidic product was 3j -hydroxy-androst-5-ene-17j -carboxylic acid. All three of these materials were then further converted by various chemical transformations into steroid hormones and synthetic analogs ... 

---