Oxidative Ring‐Expansion of a Chitin‐Derived Platform Enables Access to Unexplored 2‐Amino Sugar Chemical Space

Abstract

The chitin obtained from crustacean shell waste and other renewable resources may be used as a primary feedstock in the biorefineries of the future. Accordingly, the incorporation of chitin‐derived building blocks into new synthesis processes will accentuate the utility of this biopolymer, particularly in the production of bio‐based small molecules that contain one or more nitrogen atoms. Herein we report that enantioenriched 2‐amino sugars are readily accessible from the chitin‐derived platform 3‐acetamido‐5‐acetylfuran (3A5AF). Subjecting 3A5AF to a Noyori reduction–Achmatowicz rearrangement sequence gave N‐acetyl‐l‐rednose (RedNAc) in excellent yield and enantiopurity. Acetamide hydrolysis gave l‐rednose, a rare 2‐amino sugar found in natural anthracycline and angucycline antibiotics. RedNAc was subsequently shown to be a versatile platform from which a variety of stereochemically pure 2‐amino sugars are readily attainable. The synthesis of chiral, bio‐based N‐compounds from chitin emphasises the rapidly expanding utility of this biopolymer as a viable platform for fine chemical production.

Towards Shell Biorefinery: Advances in Chemical‐Catalytic Conversion of Chitin Biomass to Organonitrogen Chemicals

“…NAc) has been produced in satisfactory yield and enantiopurity from 3A5AF via Noyori reduction and Achmatowicz rearrangement, as shown in Scheme 11. [48] Starting from RedNAc, a few stereochemically pure 2-amino sugars were readily attainable. The subsequent acetamide hydrolysis of RedNAc gave l-rednose, a rare 2-amino sugar that has not been isolated and synthesized.…”

Escaping from Flatland: Stereoconvergent Synthesis of Three‐Dimensional Scaffolds via Ruthenium(II)‐Catalyzed Noyori–Ikariya Transfer Hydrogenation

“…[60] 2-Aminosugar N-acetyl-l-rednose 145 was readily accessed from chitin-derived 3-acetamido-5-acetylfuran 143 via Noyori-Ikariya reduction-Achmatowicz rearrangement sequence and was elaborated to versatile 2-aminosugar derivatives 146-149 ( Figure 35). [61] The somewhat forcing conditions of the Noyori-Ikariya hydrogenation might have been avoided by switching to tethered Ru II -catalysts in transferh ydrogenation mode:f or the reduction of 2-acetylfurane full conversionsw ere achieved in HCO 2 H/Et 3 Na t4 0o r6 0 8Cw ithin few hours using 0.1 mol %o ft he catalysts F, H or J,p roducing the correspondinga lcohol with 98 % ee. [62] Ap ractical access to enantiopure substituted 2-arylpiperidines with up to 4c hiral centers was developedb yT ong et al (Figure 36).…”

Making natural products from renewable feedstocks: back to the roots?

“…338,341 3A5AF (203) can in turn be converted to L-rednose (204), which contains a b-aminoenone moiety rarely seen in carbohydrates, in a three step sequence. 342 2.3.2. Natural product syntheses using chitin/chitosan derived starting materials 2.3.2.1.…”

“…A concise example is the L-rednose (L-204) building block synthesized by Sperry and coworkers from 3A5AF (203) (Scheme 32). 342 It is part of the complex tetracycline-type natural products rudolphomycin (374), 529,530 aclacinomycin X (375), 11-hydroxyaclacinomycin X (376) 531,532 as well as saquayamycins H (377) and I (378) 533,534 which have not been synthesized so far (Schemes 59 and 60). A viable synthesis of an advanced intermediate like 204 based on eco-friendly methods and starting materials already constitutes a signicant progress in the total synthesis of these compounds.…”