Stereodivergent Synthesis of Iminosugars from Stannylated Derivatives of (S)-Vinylglycinol

Abstract

An original access to iminosugars from a cis/trans mixture of stannylated oxazolidinones 5 is reported. The dehydropiperidines 7-trans and 7-cis were obtained stereoselectively with an RS and SS configuration depending on the order of the Sn-Li transmetalation (followed by electrophilic trapping) and of the ring closing metathesis reactions due to the stereoselective epimerization of the α-aminoanion intermediate. The dehydropiperidines 7-trans and 7-cis were subsequently used for the synthesis of enantiopure homonojirimycin analogs.

Sn−Li Transmetalation of α‐Aminoorganostannanes for the Stereoselective Synthesis of Substituted Dehydropiperidines and Dehydroazepanes

“…Under the same experimental conditions (-78°C, THF), the transmetalation/trapping sequence carried out on (S,S)-4a proceeded with a good yield and a very high diastereoselectivity when CO 2 (g) was the electrophile. [12] The Sn-Li exchange on (S,S)-4a followed by electrophilic trapping was also proved to be efficient with benzaldehyde, isovaleraldehyde and hexanal as electrophiles, leading selectively to (R,S) products, but as a couple of diastereomers due to the lack of diastereoselectivity on the aldehyde enantiotopic faces. The configuration of the major diastereomer of 7a was determined by X-ray diffraction analysis of suitable monocrystals and was found to be (S,R,S).…”

“…The electrophilic trapping was also achieved with CO 2 (g) and, after esterification under neutral conditions with TMSCHN 2 , 13a was obtained in 76% yield with a strong (S,S) preference [(S,S)-13a / (R,S)-13a = 97/3]. [12] We then looked at the use of aldehydes as electrophiles and, taking into account the possible occurrence of an intramolecular acyl transfer, the reaction temperature was fixed to -90°C. Starting from (R,S)-3a, the reaction products were obtained with an exclusive (S)-configuration at the previous anionic center whatever the nature of the aldehyde (benzaldehyde, isovaleraldehyde or hexanal).…”

“…[4] Following a preliminary communication, the aim of the present work is to study the Sn-Li transmetalation reaction carried out on the stannylated oxazolidinones 3 and 4 by n-butyllithium in order to evaluate its diastereoselectivity and to rationalize the obtained results (Scheme 1). [12] We first examined the transmetalation reaction of stannylated oxazolidinones 4 before considering those of 3. Scheme 1.…”

Catalytic Enantioselective Silylation of N-Sulfonylimines: Asymmetric Synthesis of α-Amino Acids from CO2 via Stereospecific Carboxylation of α-Amino Silanes

“…Thus, this synthetic strategy is of great importance not only for the utilization of CO 2 , an abundant, inexpensive, and relatively nontoxic C1 source, but also for providing a new and alternative method for the synthesis of optically active α-amino acid derivatives via carboxylation of amine derivatives. There are several methods for preparing chiral α-amino acid derivatives via both chemical and biochemical processes, among which the utilization of CO 2 is limited and mostly represented by enantioselective α-carboxylation of α-amino stannanes or alkyl amines using a combination of BuLi and an appropriate chiral amine such as (−)-sparteine. Our group already revealed that optically active N - tert -butylsulfonyl-α-amido stannanes derived from Ellman’s chiral tert -butylsulfinamide undergo stereospecific carboxylation with CO 2 using CsF to afford optically active α-amino acid derivatives .…”

Synthesis of Arylglycines from CO2 through α-Amino Organomanganese Species

“…Among the various approaches, α-amino acid synthesis through CO 2 incorporation under mild conditions is especially attractive since α-amino acids have broad applications in both biochemistry and organic chemistry . Early examples of the synthesis of α-amino acids using CO 2 were mostly represented by the carboxylation of α-amino organolithium compounds ,, and electrochemically promoted insertion of CO 2 into the CN bond . In 2011, we reported a one-pot synthesis of N -Boc-α-amino acids from N -Boc-α-amido sulfones by using a combination of TMS–SnBu 3 and CsF under CO 2 pressure (Scheme , eq 1) .…”