Cis-diastereoselectivity in pictet-spengler reactions of L-tryptophan and electronic circular dichroism studies.

The diastereoselective synthesis of optically active 1,3-disubstituted tetrahydro-ß-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-ß-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-ß-carbolines and revealed the stereochemical factors that determine the characteristic ECD data.

Methyl 2-(2-hydroxy-acetamido)benzoate.

The title compound, C(10)H(11)NO(4), was formed from 4,1-benzoxazepine-2,5(1H,3H)-dione and ammonia gas. Intra-molecular hydrogen bonding is present between the amide N-H group and the carbonyl O atom of the ester group. The crystal structure features inter-molecular O-H⋯O hydrogen bonds.

cis-(9S,10S)-Methyl 1-propyl-1,2,3,4-tetra-hydro-ß-carboline-3-carboxyl-ate.

The title compound, C(16)H(20)N(2)O(2), was synthesized from (S)-tryptophan methyl ester hydro-chloride and butyraldehyde. The absolute configuration 9S,10S was assigned on the basis of the unchanging chirality of the C9 centre. The NH group of the indole ring is involved in inter-molecular N-H⋯O hydrogen bonding, while the NH group of the six-membered ring is not. This latter ring has a half-chair conformation.

The effect of medicinal plants of Islamabad and Murree region of Pakistan on insulin secretion from INS-1 cells.

In vitro testing of the extracts of medicinal plants collected from Islamabad and the Murree region on insulin secretagogue activity was carried out. Dried ethanol extracts of all plants (ZH1-ZH19) were dissolved in ethanol and DMSO, and tested at various concentrations (between 1 and 40 microg/mL) for insulin release from INS-1 cells in the presence of 5.5 mM glucose. Glibenclamide was used as a control. Promising insulin secretagogue activity in various plant extracts at 1, 10, 20 and 40 microg/mL was found, while in some cases a decrease in insulin secretion was also observed. Artemisia roxburghiana, Salvia coccinia and Monstera deliciosa showed insulin secretagogue activity at 1 microg/mL (p < 0.05) while Abies pindrow, Centaurea iberica and Euphorbia helioscopia were active at 10 microg/mL (p < 0.05). Extracts of Bauhinia variegata and Bergenia himalacia showed effects at 20 microg/mL (p < 0.05), and Taraxacum officinale and Viburnum foetens at 40 microg/mL (p < 0.05). Insulin secretagogue activity could not be detected in the extracts of Adhatoda vasica, Cassia fistula, Chrysanthemum leucanthemum, Morus alba, Plectranthus rugosus, Peganum harmala and Olea ferruginea. The results suggest that medicinal plants of Islamabad and the Murree region of Pakistan may be potential natural resources for antidiabetic compounds.

New pregnane-type steroidal alkaloids from Sarcocca saligna and their cholinesterase inhibitory activity.

Five new steroidal alkaloids, 5,14-dehydro-N(a)-demethylsaracodine [3beta-N(a)-methyl-20S-N(b)-acetyl-N(b)-methylamino-pregn-5,14-diene] (1), 14-dehydro-N(a)-demethylsaracodine [3beta-N(a)-methyl-20S-N(b)-acetyl-N(b)-methylamino-5alpha-pregn-14-ene] (2), 16-dehydrosarcorine [(20S)-20-(N,N-dimethylamino)-3beta-(N(a)-acetylamido)-5alpha-pregn-16-ene] (3), 2,3-dehydrosarsalignone [(20S)-20-(N,N-dimethylamino)-3beta-(tigloylamino)-pregn-2,5-diene-4-one] (4), and 14,15-dehydrosarcovagine-D [(20S)-20-(N,N-dimethylamino)-3beta-(tigloylamino)-5alpha-pregn-2,14-diene-4-one] (5), were isolated from the ethanolic extract of Sarcococca saligna, along with two known bases, sarcovagenine-C (6) and salignarine-C (7). Their structures were elucidated on the basis of spectroscopic methods. All seven compounds were found to possess cholinesterase inhibitory potential in a concentration-dependent manner with the IC50 values ranging from 12.5 to 200 microM against acetylcholinesterase and from 1.25 to 32.2 microM against butyrylcholinesterase.