title: Cis-diastereoselectivity in pictet-spengler reactions of L-tryptophan and electronic circular dichroism studies.
abstract: The diastereoselective synthesis of optically active 1,3-disubstituted tetrahydro-β-carbolines using polar protic Pictet-Spengler cyclization of (S)-tryptophan methyl ester with five aldehydes RCHO (R═CH(3), C(2)H(5), C(3)H(7), C(4)H(9), and C(6)H(5)) was studied. As an alternate route, the cyclization of (S)-tryptophan with the same aldehydes and subsequent methylation of the resulting tetrahydro-β-carboline carboxylic acids were also performed for comparison. (13)C NMR and electronic circular dichroism (ECD) studies and time-dependent density functional theory ECD calculations data established the relative 1,3 cis/trans and the absolute configuration (1S,3S/ 1R,3S) of the synthesized compounds. The solid-state and solution ECD study of the prepared compounds, supported by ECD calculation and X-ray data, afforded a reliable ECD method for the configurational assignment of 1,3-disubstituted tetrahydro-β-carbolines and revealed the stereochemical factors that determine the characteristic ECD data.
authors: Allama Iqbal Open University, Department of Chemistry, Islamabad, Pakistan. naghmana.rashid@aiou.edu.pk
authors: Naghmana
authors: N
authors: Rashid
authors: Samina
authors: S
authors: Alam
authors: Mashooda
authors: M
authors: Hasan
authors: Naeema
authors: N
authors: Khan
authors: Khalid M
authors: KM
authors: Khan
authors: Helmut
authors: H
authors: Duddeck
authors: Gennaro
authors: G
authors: Pescitelli
authors: Agnes
authors: A
authors: Kenéz
authors: Sándor
authors: S
authors: Antus
authors: Tibor
authors: T
authors: Kurtán
mesh_terms: D002942:Circular Dichroism; D003500:Cyclization; D015394:Molecular Structure; D013237:Stereoisomerism; D014364:Tryptophan / Q000031:analogs & derivatives / Q000737:chemistry*
chemical_list: C028129:tryptophan methyl ester; D014364:Tryptophan