New Methods for the Synthesis of Phenypropanoic Sucrose Esters

• Main Author: Filipe, Luís
• Publication Date: 2019
• Format: Master thesis
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: http://hdl.handle.net/10362/88070
• topic: sucrose; phenylpropanoic sucrose esters; protection/deprotection; metal-chelate direct esterification; enzymatic catalysis; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Química

Phenylpropanoic sucrose esters are a class of naturally occurring molecules transversely found as active compounds in ancient Chinese medicinal plants. Such compounds are comprised of a sucrose molecule substituted with a phenylpropanoid ester in one or more hydroxyl groups. Outstanding antioxidant and antitumoral properties, amongst others, arise from this class of com-pounds. Despite their huge potential as lead-compounds, the synthesis of such molecules has been overlooked in the scientific community, mainly due to the challenging and complex nature of carbohydrate chemistry. During this work, we assayed and compared three different methodologies for the chemical synthesis of phenylpropanoic sucrose esters: protection/deprotection synthesis, metal-chelate di-rect esterification and enzymatic catalysis. The protection pathway allowed the substitution of sucrose primary hydroxyls with cinnamoyl ester bonds, as a result of the different reactivity rate of bulky silyl protecting groups. The metal-chelate direct esterification permitted the introduction of the ester bond in different positions (including secondary hydroxyls) through the use of various, yet simple, metal salts. In such case, a single reaction took place with regioselectivity. Positive conclusions are also drawn about the influence of silyl groups in such catalysis. Enzymatic catalysis, however, failed to provide any reaction product, though some progresses were made. The current work established and optimized protocols for the synthesis of phenylpropanoic esters through such techniques, which permits the creation of a large library of posible lead compounds. Natural phenylpropanoic sucrose esters, new acetylated sucrose derivatives alongside with artificial phenylpropanoic sucrose esters were synthetized as a result of the protocols developed.