Table 1. Justification of the principles of green chemistry.

Relevant Principles of Green Chemistry and analysis for the synthesis of alkoxybutenolide monomers from furfural.

Principles of Green Chemistry	Justification
Less hazardous chemical synthesis	In the synthesis, starting from the platform chemical furfural, benign solvents (methanol and toluene) are used for the preparation of alkoxybutenolides. As vacuum distillation is used as the purification method, no other environmentally hazardous solvents are used.
Design for energy efficiency	The oxidation of furfural is performed photochemically (visible light) at ambient temperature. Scalable photooxidation procedures with energy-efficient lamps (TL and LED) have been designed.
Use of renewable feedstocks	Furfural, a platform chemical derived from the acid-mediated dehydration of lignocellulose (H2O as waste), is used as sole starting material for the synthesis of alkoxybutenolides (45, 46).
Reduce derivatives	The hemiacetal moiety in hydroxybutenolide B1 allows facile derivatization toward alkoxybutenolides without the use of protecting/activation groups.
Catalysis	The oxidation of furfural is photocatalytic using molecular oxygen, preventing the use of stoichiometric amounts of oxidants.
Inherently safer chemistry for accident prevention	The flow reactor designed for the upscaling of the photooxidation of furfural allows a safer handling of reactive substrates (pressurized oxygen) or intermediates (endoperoxide) as low concentrations, and no accumulation is present in flow (30).