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

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.

Synthesis and glycogen phosphorylase inhibitory activity of N-(beta-D-glucopyranosyl)amides possessing 1,4-benzodioxane moiety.

A series of N-(beta-D-glucopyranosyl)amides 5d-i were synthesized by PMe(3) mediated Staudinger reaction of O-peracetylated beta-D-glucopyranosyl azide (1) followed by acylation with carboxylic acids 3d-i and subsequent Zemplén deacetylation. The new compounds were tested for their inhibitory activity against rabbit muscle glycogen phosphorylase and the structure-activity relationships of these compounds are also discussed in this paper.

Synthesis and structure-activity relationship study of monotesone-A, an antifungal component of Monotes engleri.

The synthesis of (+/-)-monotesone-A, an antifungal component of Monotes engleri, as well as its four structural analogues were accomplished starting from the corresponding MOM-protected phloracetophenone and benzaldehyde derivatives. Antifungal activities of the five flavanone derivatives were studied against Candida albicans (14053 and ATCC 10231), Candida inconspicua, Candida dubliniensis and Candida krusei.

Circular dichroism of diglycosyl dichalcogenides in solution and solid state.

Solution and solid-state CD spectra of nine peracetylated and deacetalyted diglycosyl disulfides were measured to study the relationship between the low-energy CD transitions (n1-->sigma*(S--S) and n2-->sigma*(S--S)) and helicity of the inherently chiral disulfide chromophore as perturbed by chiral carbohydrate moieties. The solid-state CD spectra were directly correlated with the reported X-ray structures of Ac4GlcSSGlcAc4 and Ac4GlcSSGalAc4, and the CD data revealed that all the disulfides have M helicity with C1--S--S--C1' dihedral angles -90 degrees < phi < 0 degrees both in solution and in the solid state. A TDDFT CD study was carried out on dimethyl diselenide which confirmed that the same quadrant rule is relevant between the signs of the low-energy CD transitions and the diselenide torsional angle as formulated previously for the disulfide chromophore.

[Synthesis and antifungal activity of naturally occurring O- and C-prenylated flavanones].

Flavonoids is one of the most important groups of naturally occurring O-heterocycles possessing a wide range of biological activity. O- and C-prenylated flavanones as members of flavonoids also show remarkable biological activity such as antibacterial, antiviral, anti-tumor, antifungal, anti-HIV and enzyme inhibition activity. O- and C-prenylated flavanones possessing remarkable biological activity are representatives of this family of natural products.