Aspalathin Synthesis via Sugar-Dihydrochalcone Coupling

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Solution Overview

Problem

Current methods for synthesizing aspalathin and its analogues are inefficient, requiring more than eight steps and yielding less than 2% of the compound, making them not commercially viable.

Innovation Solution

A method involving the coupling of a sugar moiety with a dihydrochalcone or chalcone, followed by further coupling with intermediates to produce aspalathin or its analogues, using protective groups and Lewis acid catalysis to enhance electrophilicity and nucleophilicity, reducing the number of steps and improving yield.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional multi-step synthesis methods are used, then aspalathin can be produced, but the number of synthesis steps exceeds eight and yield is less than 2%

Engineering Contradiction:

Improvesynthesis yieldVSAvoidnumber of synthesis steps

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The synthesis is divided into distinct modular stages: (i) formation of the chalcone intermediate, (ii) reduction to dihydrochalcone, and (iii) coupling with the sugar moiety. Each stage can be independently optimized and executed, reducing overall complexity while maintaining high yield through focused optimization of each segment.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Protecting groups are strategically installed on the sugar moiety and aromatic rings before coupling reactions. This preliminary protection prevents unwanted side reactions during subsequent steps, ensuring high selectivity and yield without requiring additional purification steps.

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If conventional synthesis methods are used, then aspalathin can be produced, but the process is not commercially viable

Engineering Contradiction:

Improvecommercial viabilityVSAvoidsynthesis yield

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The methodology employs specific parameter optimizations including Lewis acid catalyst selection (BF3·OEt2, Sc(OTf)3), solvent systems (DCM, CH3CN), and temperature control to achieve high yields. These parameter changes transform the synthesis from a laboratory-scale multi-step process to a commercially viable operation with yields exceeding 90% in key steps.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The chalcone and dihydrochalcone intermediates serve as stable, isolable compounds that facilitate the coupling reaction with sugar moieties. These intermediaries allow for streamlined processing and scale-up, making the overall process commercially viable by eliminating the need for complex in-situ transformations.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If protective groups are used in the coupling reaction, then selectivity is improved, but the number of additional steps increases

Engineering Contradiction:

Improvecoupling selectivityVSAvoidnumber of process steps

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Protecting groups (benzyl, acetate, methoxymethyl) are installed on hydroxy groups of the sugar and aromatic rings before coupling. This preliminary protection ensures high selectivity during the Lewis acid-catalyzed coupling reaction, and the groups are removed in a single final deprotection step using Pd/C hydrogenation or BBr3, minimizing additional process steps.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The protecting groups serve multiple functions: (i) preventing unwanted O-glycosylation, (ii) directing C-glycosylation to the desired position, and (iii) being removed in a single final step. This multi-functionality reduces the overall number of steps despite the initial protection requirements.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This method allows for the synthesis of aspalathin and its analogues in higher quantities and fewer steps, making the process commercially viable and efficient.

Implementation Method 1

using protective groups and Lewis acid catalysis to enhance electrophilicity and nucleophilicity

Methodology Applied

Scientific EffectLewis acid catalysis: Catalysis

Data Source

PatentUS9181293B2Method for the synthesis of aspalathin and analogues thereof

Publication Date: 2015.11.10 SOUTH AFRICAN MEDICAL RES COUNCIL

AI summary

A method of synthesising Aspalathin and its analogues or derivatives is disclosed. The method comprises synthesising a compound of formula 1 or its analogues or derivatives:whereineach of R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 is independently selected from the group consisting of —H, —OH, hydrocarbyl groups, saccharide moieties and —OR15;R15 is selected from the group consisting of hydrogen, a hydrocarbyl group (e.g. methoxy or ethoxy), an acyl group and a benzyl group; andR11, R12, R13 and R14 are independently selected from the group consisting of —H, hydrocarbyl groups, saccharide moieties, an acyl group and a benzyl group. The method comprises the step of coupling a sugar to a dihydrochalcone, chalcone or flavanone, or coupling the sugar to an intermediate for producing a dihydrochalcone, chalcone or flavanone followed by coupling of the sugar-intermediate adduct to a further intermediate for producing a dihydrochalcone, chalcone or flavanone, and transforming the product thereof into a compound of formula 1 or an analogue or derivative thereof.