A Convenient Practical Method for the Preparation of (−)-(1S,2S)-5-Norbornene-2-carboxylic Acid, Incorporating Efficient Recovery of the Chiral Auxiliary d-Pantolactone

Abstract

A convenient practical method was developed for the preparation of enantiomerically pure (−)-(1S,2S)-5-norbornene-2-carboxylic acid, wherein the chiral auxiliary d-pantolactone was recovered efficiently.

π-Stacking Effect on Levoglucosenone Derived Internal Chiral Auxiliaries. A Case of Complete Enantioselectivity Inversion on the Diels−Alder Reaction

“…Acrylate 6 and cyclopentadiene were reacted in the diverse reaction conditions compiled in Table . All cycloadditions were endo diastereoselective, as predicted by the Alder endo rule . The existence of two conformers in the acrylate 6 reflects the moderate selectivity in its Diels−Alder reaction with cyclopentadiene, which increases as the temperature of the reaction decreases.…”

Photoremovable chiral auxiliary

“…To simplify GC analysis of the mixture of stereoisomers, 40 3m-p were esterified with methanol in the presence of TsOH to the corresponding methyl esters 7m-p (Scheme 4). The absolute stereochemistry of 7 was determined by comparing it with that of the authentic compounds [41][42][43] (ESI ‡). For comparison, the methyl esters 7m-p were also directly produced by treating the Diels-Alder reaction adducts 2a, b with K 2 CO 3 in aqueous methanol.…”

Synthesis of an o-Nitrobenzyl Attached A1 Adenosine Receptor Antagonist, a Prodrug Approach

“…To the mixture of 1,3-dipropyl-5,6-diaminouracil (24 g, 0.1 mmol), o-nitrobenzyl chloride (20 g, 0.12 mol) in ethanol (400 mL) was added triethyl amine (16 g, 0.16 mol). To the solution of (À)(1S,2S)-5-norborbene-2carboxylic acid [10] (5 g, 36 mmol) in CH 2 Cl 2 (125 mL), was added dropwise diluted oxalyl chloride (5 mL in 125 mL CH 2 Cl 2 ). The mixture was extracted with ethyl acetate (2 Â 150 mL) and the organic layer was dried with MgSO 4 .…”