Francisco G. Calvo-Flores

Lignin as Renewable Raw Material

Lignin is by far the most abundant substance based on aromatic moieties in nature, and the largest contributor to soil organic matter. Millions of tonnes of several lignin preparations are produced by the paper industry every year, and a minimal amount of lignin is isolated by direct extraction of lignin from plants. Lignin is used either directly or chemically modified, as a binder, dispersant agent for pesticides, emulsifier, heavy metal sequestrant, or component for composites and copolymers. For value-added applications of lignin to be improved, medium- and long-term conversion technologies must be developed, especially for the preparation of low-molecular-weight compounds as an alternative to the petrochemical industry.

Sustainable Chemistry Metrics

Green chemistry has developed mathematical parameters to describe the sustainability of chemical reactions and processes, in order to quantify their environmental impact. These parameters are related to mass and energy magnitudes, and enable analyses and numerical diagnoses of chemical reactions. The environmental impact factor (E factor), atom economy, and reaction mass efficiency have been the most influential metrics, and they are interconnected by mathematical equations. The ecodesign concept must also be considered for complex industrial syntheses, as a part of the sustainability of manufacturing processes. The aim of this Concept article is to identify the main parameters for evaluating undesirable environmental consequences.

Lignin and lignans as renewable raw materials : chemistry, technology and applications

As naturally occurring and abundant sources of non-fossil carbon, lignin and lignans offer exciting possibilities as a source of commercially valuable products, moving away from petrochemical-based feedstocks in favour of renewable raw materials. Lignin can be used directly in fields such as agriculture, livestock, soil rehabilitation, bioremediation and the polymer industry, or it can be chemically modified for the fabrication of specialty and high-value chemicals such as resins, adhesives, fuels and greases.

Synthesis of Glycosylamines from Glycosyl Isothiocyanates and Bis(tributyltin) Oxide

The synthesis of glycopyranosylamines is described from the reaction of glycopyranosyl isothiocynates with bis(tributyltin) oxide. The method is simple and efficient allowing, under very mild conditions, the synthesis of N-acyl glycopyranosylamines in one pot. The reactions were performed using both 2-deoxy-2-iodo glycopyranosyl isothiocyanates and glycopyranosyl isothiocyanates derived from mono- and disaccharides. Anomerization was observed when the starting materials were α-glycopyranosyl derivatives. The methodology has also been applied for the preparation of several glycosyl amino acids.

Green and Bio-Based Solvents

Chemical reactions and many of the procedures of separation and purification employed in industry, research or chemistry teaching utilize solvents massively. In the last decades, with the birth of Green Chemistry, concerns about the employment of solvents and the effects on human health, as well as its environmental impacts and its dependence on non-renewable raw materials for manufacturing most of them, has drawn the attention of the scientific community. In this work, we review the concept of green solvent and the properties and characteristics to be considered green. Additionally, we discuss the different possible routes to prepare many solvents from biomass, as an alternative way to those methods currently applied in the petrochemical industry.

NMR assignment in regioisomeric hydroquinones

A set of regioisomeric pairs of tricyclic hydroquinones, analogues of antitumor 9,10‐dihydroxy‐4,4‐dimethyl‐5,8‐dihydroanthracen‐1(4H)‐one (1) and other derivatives, were synthesized and their regiochemistry and NMR spectra assigned by using 1H‐detected one‐bond (CH) HMQC and long‐range CH HMBC, in good agreement with theoretical O3LYP/Alhrichs‐pVTZ calculations. The 5‐hydroxymethyl derivatives (11, 15, 19) showed a 3JH, H coupling constant of methylene protons evidencing the presence of a seven‐membered intramolecular hydrogen bonded ring, not observed for the 8‐hydroxymethyl isomers. Copyright

SELECTIVE PIVALOYLATION AND DIPHENYLACETYLATION OF CYCLOMALTO-OLIGOSACCHARIDES

Regioselective acylation of cyclomalto-oligosaccharides was achieved using pivaloyl and diphenylacetyl chlorides. The reaction of cyclomaltohexaose (1) with pivaloyl chloride gave the hexakis(2,6-di-O-pivaloyl) derivative 19 in 66% yield. Similar reaction with cyclomalto-heptaose (2) led to the octakis(2I,6I,6II,6III,6IV,6V,6VI ,6VII-O-pivaloyl) 26 and the 17 heptakis(6-O-pivaloyl) derivatives in 34 and 26% yields, respectively. The octakis(6-O-pivaloyl) derivative 18 was the only compound isolated (72%) in the reaction of pivaloyl chloride with cyclomalto-octaose (3). Diphenylacetylation of 1-3 gave the symmetrical (20-22) and the non-symmetrical (27-29) per(6-O-diphenylacetyl) esters as major and minor products, respectively.

Expeditious synthesis of monosulfated thio-linked disaccharides

1-Thio-sugars react with cyclic sulfate sugars to give monosulfated thio-linked disaccharides regioselectively in one step; the methodology has the advantages of the easy access and stability of the reagents and the simplicity of the procedure.