Stereoselective synthesis and transformation of pinane-based 2-amino-1,3-diols

Abstract

A library of pinane-based 2-amino-1,3-diols was synthesised in a stereoselective manner. Isopinocarveol prepared from (−)-α-pinene was converted into condensed oxazolidin-2-one in two steps by carbamate formation followed by a stereoselective aminohydroxylation process. The relative stereochemistry of the pinane-fused oxazolidin-2-one was determined by 2D NMR and X-ray spectroscopic techniques. The regioisomeric spiro-oxazolidin-2-one was prepared in a similar way starting from the commercially available (1R)-(−)-myrtenol (10). The reduction or alkaline hydrolysis of the oxazolidines, followed by reductive alkylation resulted in primary and secondary 2-amino-1,3-diols, which underwent a regioselective ring closure with formaldehyde or benzaldehyde delivering pinane-condensed oxazolidines. During the preparation of 2-phenyliminooxazolidine, an interesting ring–ring tautomerism was observed in CDCl3.

An unexpected isomerisation of Isoquinuclidines

“…Such a result is rather surprising for an equimolar mixture of dienes and cannot be explained on the basis of simple stereoselection considerations. A plausible explanation could arise from the de‐epimerisation of the original diastereomeric dihydropyridines induced by the subsequent 1,4‐cycloaddition reaction 14 . In this sense, the equilibration of the original epimeric dihydropyridines would allow for a kinetic resolution favouring the formation of the major cycloadduct 2A (Scheme 4).…”

The pinene scaffold: its occurrence, chemistry, synthetic utility, and pharmacological importance

“…Myrtenol and its aldehyde derivative are key intermediates in the synthesis of bioactive aminol such as 2-phenyliminooxazolidines and spiro-fused oxazolidin-2-one. 52 The two compounds and perillyl alcohols can be easily prepared from pinene oxide. Yin and his group reported the synthesis of myternol 63 (18.6%), myternal 64 (7.1%), perillyl alcohols 65 (47%), and diol 66 (15.8%) using tetraimidazolium nitrate 67 catalyzed isomerization of pinene oxide ( Scheme 22 ).…”