Methyl propionate, alkaline hydrolysis

To set the stage for the crucial aza-Robinson annulation, a reaction in which the nucleophilic character of the newly introduced thiolactam function is expected to play an important role, it is necessary to manipulate the methyl propionate side chain in 19. To this end, alkaline hydrolysis of the methyl ester in 19, followed by treatment of the resulting carboxylic acid with isobutyl chlorofor-mate, provides a mixed anhydride. The latter substance is a reactive acylating agent that combines smoothly with diazomethane to give diazo ketone 12 (77 % overall yield from 19). 

Fig. 5-15. Correlation between g[k/krx,) and 1/sr for the alkaline hydrolysis of methyl propionate in eight acetone/water mixtures at 25 °C (o) [252], and for the Sn2 reaction between the azide anion and 1-bromobutane in six pure dipolar non-HBD solvents at 25 °C ( ) [67] (rate constants relative to the solvent with the largest dielectric constant).

Suh et al.65 have reported a formal total synthesis of Mansonone F and this is described in Scheme 12. 5-Methoxy-a-tetralone (127) was converted to 1-methyl-5-hydroxy-naphthalene (128) by the standard organic reactions. Treatment of (128) with phenyl boronic acid, paraformaldehyde and propionic acid followed by catalytic hydrogenation yielded compound (129). This on alkylation gave the compound (130) which on alkaline hydrolysis was converted to acid. The acid halide underwent intramolecular Friedal-Crafts acylation affording an intermediate (131) whose transformation to Mansonone F has been accomplished by Best and Wege.59... 

Synthesis. DL-Tryptophan is synthesized in 70% over-all yield from crude indole by the method of Albertson and Tullar (50). Ethyl o-acetamido-a-cyano-/3-(3-indolyl)-propionate (A) is prepared in 98% yield from ethyl acetamidocyanoacetate , gramine (3-dimethylamino-methyl indole) , sodium, ethanol and ethyl iodide according to the procedure described by Albertson et al. (49). OL-Tryptophan is prepared by alkaline hydrolysis of (A). Other practicable syntheses of tryptophan which have been reported recently are outlined in the following equations. 

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