Pallavi Tiwari

A one-pot conversion of artemisinin to its ether derivatives☆

Abstract A one-pot preparation of artemether, arteether and related antimalarial compounds from artemisinin, using NaBH 4 /Amberlyst-15, is reported.

Modified One‐Pot Protocol for the Preparation of Thioglycosides from Unprotected Aldoses via S‐Glycosyl Isothiouronium Salts*

An efficient one‐pot protocol for the direct preparation of thioglycosides starting from unprotected reducing sugars via S‐glycosyl isothiouronium salts is reported. In this one‐pot methodology, BF3 · OEt2 has been used as a general catalyst for both per‐O‐acetylation of sugars and conversion of sugar per‐O‐acetates into S‐glycosyl isothiouronium salts, which was allowed to react with alkylating agents in the presence of a base to furnish thioglycosides in excellent yield. *C.D.R.I. communication no. 6767. Authors contributed equally to this work.

Practical synthesis of sulfated analogs of lactosamine and sialylated lactosamine derivatives

Abstract A series of β‐D‐Gal‐(1 → 4)‐β‐D‐GlcNAc‐octyl, NeuAcα‐(2 → 3)‐β‐D‐Gal‐(1 → 4)‐β‐D‐GlcNAc‐octyl, and their 6‐O‐sulfated and 6′‐O‐sulfated analogs (1–6) were synthesized in a concise manner starting from readily accessible monosaccharide intermediates. The syntheses involved formation of an orthogonally protected disaccharide and a trisaccharide from which all six compounds were derived. #C.D.R.I. Communication no. 6456.

Synthesis and evaluation of antitubercular activity of glycosyl thio- and sulfonyl acetamide derivatives.

A series of glycosyl thioacetamide and glycosyl sulfonyl acetamide derivatives have been prepared following a convenient reaction protocol and evaluated for their antitubercular activity against Mycobacterium tuberculosis H(37)Rv. Amongst 32 compounds evaluated 3 compounds were effective in inhibiting mycobacterial growth at MIC of 6.25 microg/mL, 6 compounds at MIC of 3.125 microg/mL and 1 compound at MIC of 1.56 microg/mL. All active compounds were found nontoxic in Vero cell lines and mice bone marrow macrophages.

Synthesis of oligosaccharide fragments corresponding to the exopolysaccharide released by Streptococcus macedonicus Sc 136.

Hexa-, penta- and tetrasaccharide fragments related to the repeating unit of the exopolysaccharide secreted by Streptococcus macedonicus Sc 136 were synthesized in a very efficient manner involving minimum number of steps. A general glycosylation condition has been applied for all glycosylation steps and yields were excellent.

Unprecedented Transformation of Thioglycosides to Their Corresponding 1‐O‐Acetates in the Presence of HClO4‐SiO2 §

An unprecedented conversion of thioalkyl/aryl glycoside to the corresponding 1‐O‐acetates has been described using acetic anhydride and HClO4‐SiO2 at rt. Although this transformation does not play an important role in the oligosaccharide synthesis in comparison to its reverse transformation, this gives useful information in selecting the reaction condition for the synthesis of oligosaccharides. The yields were excellent in all cases. §C.D.R.I. communication no. 6979.

Synthesis of a Pentasaccharide Repeating Unit of the Extracellular Polysaccharide Produced by Lactobacillus Delbrueckii Subsp. Bulgaricus 291

A pentasaccharide methyl glycoside has been synthesized efficiently using a modified glycosylation strategy. This pentasaccharide is a repeating unit of the exopolysaccharides produced by Lactobacillus delbrueckii subsp. bulgaricus 291.