Enantioselective synthesis of amino acids from pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione

Martins, Charles Ferreira; Viljoen, A. M.; Kruger, Hendrik G.; Fourie, L.; Roscher, Justus; Joubert, None A; Wessels, Philippus L.

doi:10.1016/s0040-4020(00)01140-6

Cited by 25 publications

(28 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The 13 C NMR spectrum exhibits a characteristic 10 amide carbonyl signal (C-4 0 at 177.50 ppm) and a urea carbonyl group (C-2 0 at 157.05 ppm), the eight methine carbons of the cage between 39.57 and 55.67 ppm and the presence of two methylene carbons at 32.95 and 33.49 ppm. Two-dimensional NMR techniques were essential for the full elucidation of the trishomocubane hydantoin.…”

Section: Resultsmentioning

confidence: 99%

“…10,15,19 It was therefore decided to investigate the feasibility of a milder alternative method of hydantoin hydrolysis. Kubik et al 21 modified a method that hydrolysed lactams and secondary amides 22 and developed an efficient, facile method for hydrolysis of˛,˛-disubstituted hydantoins.…”

Section: Resultsmentioning

confidence: 99%

“…15 This method was previously successfully applied to adamantanone 19 and to pentacyclo-undecanone. 10 As a result of the unique D 3 symmetry 14 of the trishomocubane cage skeleton, only two enantiomers of the hydantoin 3 are obtained as a racemate (see Fig. 3).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Complete NMR elucidation of a novel trishomocubane hydantoin and its mono‐ and bis‐t‐Boc protected derivatives

Fourie¹,

Govender²,

Hariprakasha³

et al. 2004

Magnetic Reson in Chemistry

Self Cite

View full text Add to dashboard Cite

The syntheses of a novel trishomocubane hydantoin and its mono- and bis-protected t-Boc derivatives are described. The less nucleophilic N-3' nitrogen of the hydantoin ring is protected first when treated with di-tert-butyl dicarbonate (t-Boc anhydride), possibly owing to steric hindrance by the bulky trishomocubane cage skeleton. More basic conditions were required to form the bis-protected t-Boc hydantoin with the same reagent. The structures of these novel compounds were elucidated with 2D NMR techniques. The proton spectrum of the trishomocubane skeleton is complex owing to major overlap of proton signals. A high-level DFT calculation was used to determine some of the crucial interatomic positions, which assisted with the elucidation of the structures. The assignment of proton and carbon signals of the three structures is described and it differs significantly from each other and also from the trishomocubanol precursor. The bis-Boc hydantoin is required for a more facile hydrolysis to the corresponding trishomocubane amino acid at room temperature.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Complete NMR elucidation of a novel trishomocubane hydantoin and its mono‐ and bis‐t‐Boc protected derivatives

Fourie¹,

Govender²,

Hariprakasha³

et al. 2004

Magnetic Reson in Chemistry

Self Cite

View full text Add to dashboard Cite

show abstract

“…0 3,10 .0 5,9 ] undecane (trishomocubane) was first reported by Eaton et al [1]. As part of a project to synthesise pentacycloundecane derived cage amino acids [2][3][4][5], the synthesis of racemic trishomocubane hydantoin 2 [6] and the corresponding amino acid 3 was undertaken (see Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Complete NMR Elucidation of Two N-Protected Trishomocubane Hydantoins and the Ethyl Ester of the Corresponding Amino Acid

2005

View full text Add to dashboard Cite

In an attempt to resolve a racemic mixture of a trishomocubane hydantoin, the synthesis of a pair of novel diastereomers was obtained by protecting the racemic hydantoin with chlorocarbonic acid-(−)(R)-sec-butyl ester. An achiral i-propyl ester was first used to establish the procedure. The NMR elucidation of both the chiral and achiral N-protected hydantoins is described. Some proton and carbon NMR shifts on the cage are reversed when relative small changes on the protection group are introduced. The chiral centre on the protective group induced splitting of some carbon signals in the 13 C spectrum on the cage skeleton, but effective separation of the diastereomers could not be obtained. In a further attempt to demonstrate the potential use of the trishomocubane amino acid in peptide synthesis, the ethyl ester of the cage amino acid was synthesised. The structures of the amino acid derivatives were elucidated with 2D NMR techniques and the assignment of the NMR data is presented.

show abstract

“…Protons on the cage are normally deshielded if a heteroatom of a side chain is positioned such that the electron rich heteroatom is in close proximity of the cage proton(s). [4,19,28,29] It is possible that the OH and NH 2 groups in 1 cause intramolecular hydrogen bond interactions. This will largely 'tie' the two groups together at room temperature.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and NMR assignment of pentacycloundecane precursors of potential pharmaceutical agents

Onajole

Makatini

Gasqui

et al. 2010

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

The synthesis and complete NMR elucidation of eight novel pentacycloundecane (PCU) derivatives are reported. These compounds are precursors in the synthesis of PCU-based anti-tuberculosis (TB) agents and potential human immunodeficiency virus (HIV) protease inhibitors. Two-dimensional (2D) NMR techniques were used to assign the NMR spectra for these compounds. Substitution of the cage molecule at (C-8/11) further complicates the assignment, since some of the substituted alkyl chain groups overlap with the cage proton signals. The side chain heteroatoms also introduce a rare through-space deshielding effect to some of the carbon atoms of the cage skeleton. Ring strain in the rigid cage skeleton appears to induce drastic electronic changes in some parts of the cage framework. This observation is more dramatic for the C-4 methylene group of the cage diols and the cage ethers.

show abstract

Enantioselective synthesis of amino acids from pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione

Cited by 25 publications

References 19 publications

Complete NMR elucidation of a novel trishomocubane hydantoin and its mono‐ and bis‐t‐Boc protected derivatives

Complete NMR elucidation of a novel trishomocubane hydantoin and its mono‐ and bis‐t‐Boc protected derivatives

Complete NMR Elucidation of Two N-Protected Trishomocubane Hydantoins and the Ethyl Ester of the Corresponding Amino Acid

Synthesis and NMR assignment of pentacycloundecane precursors of potential pharmaceutical agents

Contact Info

Product

Resources

About