Isolation from Stevia rebaudiana of DMDP acetic acid, a novel iminosugar amino acid: synthesis and glycosidase inhibition profile of glycine and \u03b2-alanine pyrrolidine amino acids

R Fernando Martínez,Jackie Hollinshead,Robert J Nash,Mark R Wormald,George W J Fleet,Sarah F Jenkinson,Atsushi Kato,Shinpei Nakagawa

doi:10.1007/s00726-019-02730-5

Abstract

DMDP acetic acid [N-carboxymethyl-2,5-dideoxy-2,5-imino-d-mannitol] 5 from Stevia rebaudiana is the first isolated natural amino acid derived from iminosugars bearing an N-alkyl acid side chain; it is clear from GCMS studies that such derivatives with acetic and propionic acids are common in a broad range of plants including mulberry, Baphia, and English bluebells, but that they are very difficult to purify. Reaction of unprotected pyrrolidine iminosugars with aqueous glyoxal gives the corresponding N-acetic acids in very high yield; Michael addition of both pyrrolidine and piperidine iminosugars and that of polyhydroxylated prolines to tert-butyl acrylate give the corresponding N-propionic acids in which the amino group of β-alanine is incorporated into the heterocyclic ring. These easy syntheses allow the identification of this new class of amino acid in plant extracts and provide pure samples for biological evaluation. DMDP N-acetic and propionic acids are potent α-galactosidase inhibitors in contrast to potent β-galactosidase inhibition by DMDP.

Highlights

Many iminosugars, sugar mimics in which the ring oxygen of a pyranose or furanose is replaced by nitrogen to form polyhydroxylated pyrrolidines [e.g. DMDPHandling Editor: W
This paper describes (a) the isolation of DMDP acetic acid 5 from Stevia in which the amino group of glycine is incorporated into the hydroxylated pyrrolidine ring, (b) the efficient conversion of the unprotected pyrrolidine iminosugars DMDP 1, DAB [1,5-dideoxy1,5-imino-d-arabinitol] 7 and galacto-DMDP [2,5-dideoxy2,5-iminogalactitol] to pyrrolidine acetic acids 5, 8, and by treatment with aqueous glyoxal, (c) Michael addition of unprotected pyrrolidine 5, 7, 10 and piperidine DNJ 2 iminosugars and the sugar amino acids 13 and 16 to tertbutyl acrylate to give N-propionic acid derivatives in which the amine of β-alanine is incorporated into the heterocyclic ring, and (d) the effect of the N-glycine and N-β-alanine sidechains on glycosidase inhibition, in particular on the change in α- and β-galactosidase activity
The iminosugar content can be as high as 0.5% of stevia leaves and comprises mainly DMDP 1; some 2 g of DMDP along with 50 mg of DMDP acetic acid 5 were isolated from 2.2 kg of leaves from Stevia rebaudiana Betoni (Asteraceae), a herb native to South America

Summary

Introduction

Sugar mimics in which the ring oxygen of a pyranose or furanose is replaced by nitrogen to form polyhydroxylated pyrrolidines [e.g. DMDP. Than their iminosugar analogues due to the high content of acidic and neutral amino acids in plants. DMDP 1 is the most widely occurring iminosugar; GCMS studies on a number of diverse plant extracts from Stevia rebaudiana, mulberry, and bluebell (Hyacinthoides non scripta) show that N-alkylated amino acids such as DMDP acetic 5 and DMDP propionic 6 acids are present (Gallagher and Yu 2014; Nash et al 2018; Wilson et al 2010). This paper describes (a) the isolation of DMDP acetic acid 5 from Stevia in which the amino group of glycine is incorporated into the hydroxylated pyrrolidine ring, (b) the efficient conversion of the unprotected pyrrolidine iminosugars DMDP 1, DAB [1,5-dideoxy1,5-imino-d-arabinitol] 7 and galacto-DMDP [2,5-dideoxy2,5-iminogalactitol] to pyrrolidine acetic acids 5, 8, and by treatment with aqueous glyoxal, (c) Michael addition of unprotected pyrrolidine 5, 7, 10 and piperidine DNJ 2 iminosugars and the sugar amino acids 13 and 16 to tertbutyl acrylate to give N-propionic acid derivatives in which the amine of β-alanine is incorporated into the heterocyclic ring, and (d) the effect of the N-glycine and N-β-alanine sidechains on glycosidase inhibition, in particular on the change in α- and β-galactosidase activity

Results and discussion

Conclusions

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