CiNii Fulltext PDF
A series of polyoxygenated cyclohexenoid natural products have been synthesized diastereo-and enantio-selectively in an integrated manner starting from either a synthetic equivalent of chiral cyclohexane-2,5-diene-1,4-diol 2 or a synthetic equivalent of chiral 4-hydroxy-2-cyclohexenone 3 obtained from the meso precursor 1. Thus, starting with (+)-2, all diastereomers of conduritols, including natural conduritols, A 14 and (-)-F 23 as well as unnatural conduritols, D 19, (+)-B 28, (-)-E 25, and (+)-C 32, have been synthesized diastereoselectively in an integrated manner on the basis of the inherent convex-face selectivity exerted by the starting material. Moreover, the same inherent stereochemical nature of (+)-2 has been reflected for the diastereocontrolled construction of some naturally occurring cyclohexenethanol derivatives isolated from some medicinal plants, (-)-cleroindicin E 39, (-)-cleroindicin C 40, and (-)-isocleroindicin E 41, to determine their absolute configuration through the common intermediate (+)-38. (+)-38 has also served as the key intermediate for the diastereocontrolled construction of non-chiral natural products rengyoxide 43, rengyol 44, and cleroindicin A 46 having meso structure. One the other hand, the chiral ketone (-)-3 obtained by the catalytic procedure has been found to serve as an appropriate stating material for the integrated construction of (-)-quinic acid 55 and (-)-shikimic acid 59, occurring in both plants and microorganisms, through the common intermediate 51 on the basis of the same stereochemical background as 2. The enantiomeric α-hydroxyketone (+)-48, generated from the enantiomeric ketone (+)-3, has also been found to serve as an appropriate starting material for the construction of the four cyclohexanemethanol dibenzoate natural products, (-)-zeylenol 66, (+)-pipoxide 67, (-)-tonkinenin A 68 and (-)-varigranol G 69. All of these have been synthesized for the first time from (+)-3 on the basis of its inherent stereochemical nature via the common bromo-ether intermediate 61.