Macrocyclic Oligoesters Incorporating a Cyclotetrasiloxane Ring

Area of Science:

• * Organic Chemistry
• * Polymer Chemistry
• * Biocatalysis

Background:

• * Macrocyclic oligoesters are synthesized via lipase-mediated transesterification.
• * Cyclotetrasiloxane cores form the basis for tricyclic and pentacyclic structures.
• * Understanding synthesis parameters is crucial for controlling macrocycle formation.

Purpose of the Study:

• * To identify major macrocyclic oligoester components in lipase-mediated transesterification.
• * To investigate the influence of solvent hydrophobicity and temperature on macrocycle synthesis.
• * To determine the effect of substrate chain length and lipase type on macrocycle yield.

Main Methods:

• * Lipase-mediated transesterification using cyclotetrasiloxane cores.
• * Screening of solvents with varying log P values (2-3 optimal).
• * Temperature variation studies (including 100 °C) and substrate chain length optimization.
• * Langmuir isotherm analysis of resulting monolayers.

Main Results:

• * Tricyclic and pentacyclic macrocyclic oligoesters were identified as major products.
• * Moderately hydrophobic solvents (log P 2-3) favored synthesis.
• * Higher temperatures (100 °C) increased smaller macrocycles at the expense of larger ones.
• * Longer chain length esters and diols promoted macrocycle synthesis with immobilized lipase B (N435).
• * Monolayer collapse mechanism differed from linear polysiloxanes.

Conclusions:

• * Solvent hydrophobicity and temperature are key factors in controlling macrocyclic oligoester synthesis.
• * Substrate structure significantly impacts macrocycle formation with specific lipases.
• * The study provides insights into the formation and properties of siloxane-based macrocycles.