Microwave Pyrolysis to Produce Levoglucosenone (LGO) and (S)-γ-Hydroxymethyl-α,β-Butenolide (HBO) from Plant Feedstocks

In our efforts to synthesize a library of modified nucleosides and oligonucleotides, variety and large quantity of the synthons and building blocks are required. To meet these needs, developing a simple and lower cost synthetic method is critical. Conventional fabrications of the key intermediates (S)-γ-hydroxymethyl-α,β-butenolide (HBO) and its procures levoglucosenone (LGO) drawn our attention, particularly from diversity of carbohydrates resources. Certainly, these two α,β-unsaturated lactone, D-ribonolactone can be obtained either from multistep synthesis, or from natural resources in fashion of pyrolysis. Nevertheless, both approach costs are relatively high because of multistep reactions, energy consumption and unsatisfied pyrolytic efficiency, difficulty of purification, as well as lower yield. Unlike traditional pyrolysis harsh conditions, this report provides a microwave (MW) method that implemented in two similar conditions, firstly, in microwave reactor pyrolysis taken place in the presence of PEG200 and acids under vacuum distillation. The process was completed rapidly, giving LGO as a major fraction. Secondly, Using PEG400 as the medium, two steps heating given LGO even better. Consequently, LGO and HBO can be obtained from cellulose, glucose, granulated sugar, soluble starch, and caster sugar, while LG can be directly synthesized from corn starch. Acidic catalysts are phosphoric acid and toluene sulfonic acid, both showed identical results. Accordingly, this method provides high proficiency, novel, facile, environmental friend, and economic approach to obtain these valuable chiral precursors for numerous bioactive compounds, pharmaceutical ingredients and materials constructions.