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The Absolute Configuration of the (+)- and (−)-cis- and (+)- and (−)-trans-1-Benzyl-4-hydroxypiperidine-3-methanols: An Unusual Application of the 1H-NMR-Mosher Method

✍ Scribed by Christian Clerc; Igor Matarazzo; Peter Rüedi

Publisher
John Wiley and Sons
Year
2009
Tongue
German
Weight
321 KB
Volume
92
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

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The enantiomerically pure title compounds were prepared and the absolute configurations assigned by the high‐field ^1^H‐NMR application of the Mosher method on the bis‐MTPA derivatives (MTPA=α‐methoxy‐α‐(trifluoromethyl)benzeneacetic acid). The final evidence for the adaptability of the procedure was effected by X‐ray crystallographic analyses. The absolute configurations of the cis‐ and trans‐1‐benzyl‐4‐hydroxypiperidine‐3‐methanols are as follows: (+)‐(3__S,4__S) and (−)‐(3__R__,4__R__) (cis), and (+)‐(3__R__,4__S__) and (−)‐(3__S__,4__R__) (trans), respectively (Scheme 2). Nonfermenting bakers' yeast reduction of methyl 1‐benzyl‐4‐oxopiperidine‐3‐carboxylate afforded (+)‐methyl (3__R__,4__S__)‐1‐benzyl‐4‐hydroxypiperidine‐3‐carboxylate (de>97%, ee>99%) which was further reduced to the (+)‐(3__S__,4__S__)‐diol (Scheme 3). The result confirms the stereochemical outcome of the biological reduction with re‐face selectivity and cis‐diastereoselectivity as predicted for bakers' yeast. The 4‐hydroxypiperidine‐3‐methanols are the key starting compounds for the synthesis of the enantiomerically pure P(3)‐axially and P(3)‐equatorially substituted cis‐ and trans‐configurated 8‐benzyl‐2,4‐dioxa‐8‐aza‐3‐phosphadecalin 3‐oxides (=8‐benzyl‐2,4‐dioxa‐8‐aza‐3‐phospha‐bicyclo[4.4.0]decane 3‐oxides) representing γ‐homo‐acetylcholine mimetics.

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