- Mono C-alkylation and mono C-benzylation of barbituric acids through zinc/acid reduction of acyl, benzylidene, and alkylidene barbiturate intermediates
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Through systematic exploration of reaction conditions, very efficient preparative procedures for obtaining large quantities of substituted 5-alkyl and 5-benzylbarbituric acids were developed. The procedure involves a two step preparation in which the second step is zinc dust/acid reduction. For preparation of 5-alkylbarbiturates, the first step is the preparation of either 5-acyl or 5-alkylidenebarbiturate. If 5-benzylbarbiturate is the target product, then the first step includes the preparation of 5-benzylidene. Regardless of the nature of the first step, all reactions presented synthetic yields around 90% and isolation and purification involves only crystallization.
- Jursic, Branko S.,Stevens, Edwin D.
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p. 2203 - 2210
(2007/10/03)
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- Convergent functional groups. 10. Molecular recognition of neutral substrates
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In this paper synthetic molecular clefts with functional groups complementary to adenines, diketopiperazines, and barbiturates are described. Lactams and imides are compared for hydrogen-bonding affinites toward each other and to the heterocycles mentioned above. Titrations in CDCl3 using NMR show association constants vary by factors of 104 for adenines, 102 for diketopiperazines, and 10 for barbiturates with the new receptors. Enantioselective recognition of cyclo-L-Leu-Leu is observed, corresponding to ΔΔG = 2.7 kcal/mol. The relative strengths of hydrogen-bonding arrays are interpreted in terms of secondary interactions such as defined in the following paper in this issue by Jorgensen and Severance.
- Jeong,Tjivikua,Muehldorf,Deslongchamps,Famulok,Rebek Jr.
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p. 201 - 209
(2007/10/02)
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- Reduction of Isopropylidene Acylmalonates, 5-Acylbarbituric Acids, and 3-Acyl-4-hydroxycoumarins to the Corresponding Alkyl Derivatives by Sodium Cyanoborohydride-Acetic Acid
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Isopropylidene acylmalonates, 5-acylbarbituric acids, and 3-acyl-4-hydroxycoumarins are readily reduced to the corresponding alkyl derivatives by sodium cyanoborohydride-acetic acid.The cyclic substrates are readily prepared by the acylation of isopropylidene malonate, barbituric acid (or its N,N'-dimethyl derivative), and 4-hydroxycoumarin, according to procedures developed by other workers.The reductions take place upon addition of a 2 mol equiv of sodium cyanoborohydride to a mixture of the acyl compound and acetic acid.This reductive transformation completes a synthetic method for the preparation of the alkyl derivatives starting from the parent compound.
- Nutaitis, Charles F.,Schultz, Rose Ann,Obaza, Judy,Smith, Francis X.
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p. 4606 - 4608
(2007/10/02)
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