Cyanoethyl ester hydrogenation

In another experiment (14), 6.4 g. of cyanoethyl ester was reduced to i3-alanine by hydrogenation at room temperature and atmospheric pressure with a catalyst containing 30 mg. of palladium and 500 mg. of polyvinyl alcohol. 

Cyanoethyl groups can be conveniently reduced to 2-aminoethyl groups using Raney nickel-hydrogen to give 2-aminoethyl-substituted ortho esters [149] (Eq. 49). 

Formulate mechanisms for all the hydrolysis reactions that effect deprotection of the solid-phase supported dinucleotide in the scheme at the bottom of p. 1209. [Caution The cyanoethyl protecting group is not removed by nucleophilic hydrolysis of the phosphate ester, because such a process would cleave all P-0 bonds indiscriminately. Can you imagine another way Hint Like other carboxylic acid derivatives (Section 20-1), the a hydrogen in nitriles is acidic.]... 

The Birch reduction of compound (322) led to the keto acid (325), identical with the intermediate obtained in the synthesis of steroid compounds by the CD — B route (Chapter IV, Scheme 117). However, the low yield of this acid and the nonstereospecificity of the construction of ring A from it (cf. [44]) made it necessary to search for more convenient methods for passing from the acid (322) to the steroids. It was found possible by de-methylation and catalytic hydrogenation to obtain from (322) one isomer of the hydroxyacid (323), the methylation and oxidation of which gave the keto ester (324). Its cyanoethylation and subsequent hydrogenolysis led to the required lOjS-isomer of the diacid (327) [417], from which it was possible to obtain etianic acid (326) by epimerization at Cg and the formation of ring A (cf. Scheme 77). 

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