From propanedioate esters

Two closely related methods for the diastereoselective preparation of <5-oxo esters have been developed. The first method uses the chelated lithio enamine 2. These Michael donors are readily available from the tert-butyl ester of L-valine and jS-oxo esters. The Michael addition of this lithio enamine 2 to 2-(arylmethylene)propanedioates, followed by hydrolytic removal of the auxiliary, provides d-oxo esters with contiguous quaternary and tertiary carbon centers with high diastereoselectivity59 60. 

A)-alcohol (7) by Sphingomonas paucimobilis SC 16113 (Fig. 6) (2) the enzymatic resolution of racemic (a-methyl)phenylalanine amide (8) and a-(4-methoxyphenyl)alanine amide (10) by amidase from Mycobacterium neoaurum ATCC 25795 to prepare the corresponding (S)-amino acids (9) and (11), and (3) the asymmetric hydrolysis of methyl-(4-methoxyphenyl)-propanedioic acid, diethyl ester (12), to the corresponding (X)-monoester (13) by pig liver esterase (Fig. 7). 

Malonic ester synthesis Synthesis of 2,2-disubstituted carboxylic acids from diethyl propanedioate Imitlonic ester). 

Loss of CO2 occurs readily only from the neutral carboxylic acid. If the ester is hydrolyzed with base, acid must be added to protonate the resulting carboxylate salt in order for decarboxylation to occur. Decarboxylation of substituted propanedioic (malonic) acids follows the same mechanism. 

Propose a synthesis of veronal from diethyl propanedioate (malonic ester. Section 23-2) and urea (Section 20-6). (Hint In the presence of a base, such as an alkoxide, amides are in equilibrium with the corresponding amidates Section 20-7.)... 

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