Enabling technologies and green processes in cyclodextrin chemistry

Abstract

SummaryThe design of efficient synthetic green strategies for the selective modification of cyclodextrins (CDs) is still a challenging task. Outstanding results have been achieved in recent years by means of so-called enabling technologies, such as microwaves, ultrasound and ball mills, that have become irreplaceable tools in the synthesis of CD derivatives. Several examples of sonochemical selective modification of native α-, β- and γ-CDs have been reported including heterogeneous phase Pd- and Cu-catalysed hydrogenations and couplings. Microwave irradiation has emerged as the technique of choice for the production of highly substituted CD derivatives, CD grafted materials and polymers. Mechanochemical methods have successfully furnished greener, solvent-free syntheses and efficient complexation, while flow microreactors may well improve the repeatability and optimization of critical synthetic protocols.

Efficient mechanochemical synthesis of regioselective persubstituted cyclodextrins

“…Ball mill assisted syntheses are good alternatives to overcome solubility difficulties in syntheses or isolation of natural compounds from vegetables using CDs [9–10]. Environmentally benign synthetic methods of CD derivatives have been recently reviewed [11]. …”

New Lipidyl-Cyclodextrins Obtained by Ring Opening of Methyl Oleate Epoxide Using Ball Milling

“…Even after 75 min, we did not see the formation of the expected product. Finally, we attempted the ring opening of epoxide using ball milling, a mecanosynthesis technique widely used in green chemistry [12,13]. Very recently, Cravotto et al [14] described ring opening of low-boiling epoxides by CDs under high-energy ball milling conditions and in the presence of NaOH, leading to well-known HP-β-CD, HP-γ-CD and epichlorhydrin cross-linked CDpolymers.…”

“…The different strategies envisaged to carry out the opening reaction of the epoxide obtained by CDs is described. Indeed, activation modes such as ultrasound [8,9], microwaves [10,11], or mechanochemistry [12] are considered as useful green tools for the chemical modification of cyclodextrins. Cravotto et al reported some works where ball milling is used to obtain well-known CD derivatives but under green and solventless conditions and with better yields [13,14].…”

Cassava Bagasse as a Substrate to Produce Cyclodextrins

“…In the production of cyclodextrins (CDs), the main substrates used are starches and their derivatives. The catalytic action of the enzyme cyclomaltodextrin‐glucan transferase (CGTase) originates a mixture of malto‐oligaccharides of cyclic structure, mainly α‐CD (cyclohexamylose), β‐CD (cycloheptamylose) and γ‐CD (cyclooctamylose), and minimal amounts of larger CDs . The CDs produced from the starch by the action of CGTase have high added value and present numerous possibilities of industrial applications due to its capacity to form inclusion complexes with organic and inorganic molecules.…”