A multikilogram-scale synthesis of l-lyxonolactone-2,3-O-isopropylidene is reported. It proceeds efficiently from an optimized, large-scale, aqueous bromine oxidation of d-ribose to
d-ribonolactone including a one-pot isopropylidene formation,
and subsequent conversion of the d-ribonolactone-2,3-O-isopropylidene to l-lyxonolactone-2,3-O-isopropylidene via the
derived C5-mesylate and intramolecular relactonization of the
product of aqueous potassium hydroxide cleavage of the
d-ribonolactone ring. The inversion of configuration at the C4-chiral center is understood in terms of an intermediating C4−C5-epoxide. The overall process is noteworthy for its operational
simplicity, stereochemical integrity, and use of inexpensive
chemicals.
Emergence of chloroquine (CQ) resistant Plasmodium falciparum strains necessitates discovery of inexpensive antimalarial drugs capable of targeting CQ-resistant strains. Towards this objective, herein we have synthesized and characterized naphthalene-Schiff bases or naphthalene-amine phenols. Among these compounds, 7 demonstrated a significant bioactivity with a half-maximal inhibitory concentration (IC(50)) of 1.7 microM against CQ-resistant Dd2 strains.
Oxidation of anthranilamides, salicylamides and some b-substituted amides with iodobenzene diacetate in methanolic potassium hydroxide led to a new and convenient synthesis of 2-benzimidazolones, 2-benzoxazolones and related compounds, respectively. The reaction probably occurs via initial Hofmann-type rearrangement followed by intramolecular cyclization of intermediate isocyanate.
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