Synthesis of the necine base (−)-supinidine from (S )-glutamic acid

Abstract

A route is described towards the pyrrolizidine † nucleus from derivatives of 5-acetylpyrrolidin-2-one using an intramolecular Wittig reaction with vinylphosphonium salts. The acetoxy ketone 15, derived from (S)-N-benzyloxycarbonylpyroglutamic acid, ‡ affords 16, a known precursor of (Ϫ)-supinidine.

Quantification of 2-acetyl-1-pyrroline in rice by stable isotope dilution assay through headspace solid-phase microextraction coupled to gas chromatography–tandem mass spectrometry

“…NDeacetylation was performed in a basic medium (Na 2 CO 3 ) leading to 2 in 48% yield. Therefore, the aforementioned 5-acetylpyrrolidin-2-one 2 [38] was prepared in 2 steps with an overall yield of 37%. Reduction of 2 by LiAlD 4 led to 3 (as a mixture of diastereoisomers) deuterated both on the pyrrolidine ring (C2) and on the lateral chain, owing to the simultaneous reduction of both amide and acetyl carbonyl groups.…”

Synthetic Strategies towards the Azabicyclo[3.3.0]-Octane Core of Natural Pyrrolizidine Alkaloids. An Overview

“…Hewson and his group reported the preparation synthesis of sulpinidine applying the same approach via a Wittig-process. A known precursor -(S)-5,6,7,7a-tetrahydro-1-acetoxymethylpyrrolizin-5(3H)-one -was prepared (84%) and easily converted to the desired PA. 217 …”

Ring Closure Reactions in Heterocyclic Systems with Implementation of Wittig and aza-Wittig Reactions

“…These authors treated the fivemembered lactone 18 with a combination of triphenylphosphine and DMAD to yield an intermediate (19) which underwent intramolecular cyclization to afford a mixture of stereoisomers 20 and 21. Various substituted analogs have been subjected to this transformation.…”

“…Also a five membered N-heterocycle was synthesized with the help of the Wittig reaction by Boynton et al [19]. The 2-acetylpyrrolidinone 50 was treated with triphenylvinylphosphonium salt to afford -via a Wittig product intermediate -new pyrrolizines (Scheme 11).…”