Abstract
A practical and robust synthetic method to obtain the natural disaccharide sambubiose (2-O-β-D-xylopyranosyl-D-glucopyranose) is reported, exploring the key step in the synthesis, i.e., stereoselective O-glycosylation. Specifically, the best combinations of glycoside donors and acceptors were identified, stereospecific control of the reaction was achieved by screening several catalysts and protection/deprotection steps were evaluated and improved. The best result was obtained by coupling allyl 3,5,6-tri-O-benzyl-β-D-glucofuranoside with 2,3,4-tri-O-acetyl-D-xylopiranosyl-α-trichloro acetimidate in the presence of trimethylsilyl triflate as a catalyst giving the corresponding protected target compound as a correct single isomer. The latter was transformed accordingly into the desired final product by deprotection steps (deallylation, deacetylation, and debenzylation). Sambubiose was synthesized into a satisfactory and higher overall yield than previously reported and was also characterized.
Highlights
IntroductionChemopreventive phytochemicals phytochemicals(CPs)(CPs)occur occurnaturally naturallyininsome someplants plants and have been shownChemopreventive and have been shown to to inhibit levels of carcinogenesis in both in vitro and vivo models AmongCPs, flavonoid inhibit all all levels of carcinogenesis in both in vitro and in in vivo models [1].[1].CPs, flavonoid (Figure1), which is constituted by carbohydrate and aglycone
The study started with the optimization of the key step, consisting of the O-glycosylation reaction between the appropriately protected glucose and protected/activated xylose
All the prepared glycoside donors and acceptors were reacted in different conditions in stereocontrol, and reproducibility was obtained by reacting donor 14a and acceptor 12b promoted the presence of powdered molecular sieves (MS) 4Å (Scheme 4) at −20 °C, and the main results are by TMSOTf
Summary
(CPs)occur occurnaturally naturallyininsome someplants plants and have been shown. CPs, flavonoid inhibit all all levels of carcinogenesis in both in vitro and in in vivo models [1].[1]. Sambubiose, on the other hand, is formed by glucopyranose and xylopyranose units linked through a 1,2-trans bond in 2-position and was first isolated as a component of anthocyanins from through a 1,2-trans bond in 2-position and was first isolated as a component of anthocyanins from elderberry (Sambucus nigra) [5], a plant with therapeutic properties [6,7]. Erbing and Lindberg [10] used a stoichiometric amount of mercuric cyanide as a cyanide as a glycosylation This reactant be used because of its hightoxicity toxicity and glycosylation promoter. Glycosylation between theglucose appropriate protected glucose and activated/protected xylose) must In be particular, the leaving group of the donor should be screened, and the correct catalyst/promoter should thoroughly explored. As a part of our ongoing investigations of disaccharide chemistry [13,14,15,16], we describe an efficient synthetic method that allowed us to obtain sambubiose in a satisfactory and higher overall protection and deprotection of functional groups which guide the regioselective reaction progress
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
