D,L-1,2,4-butanetriol can be made in two different ways; the first way is commercial synthesis through reduction of esterified D,L-malic acid with sodium borohydride, NaBH4, while the second way involves microbes. The latter method was the focus of the journal article. Nitration of racemic D,L-1,2,4-butanetriol results in D,L-1,2,4-butanetriol trinitrate, a compound that is the energetic equivalent of nitroglycerin, but is less shock sensitive, more thermally stable, and less volatile. One of the final steps in the synthesis of D, L-1,2,4-butanetriol via microbes is the reduction of a racemic mixture of D,L-3,4-dihydroxybutanal (aldehyde), to the final alcohol product, as seen in the reaction below. The catalyst for the reaction is dehydrogenase from E. coli.

Dimethyl ether (DME) is a multipurpose clean fuel and chemical feedstock that can be produced from a wide variety of of sources and has a number of important applications. About 10,000 tons of DME are manufactured each year for uses in cosmetics and aerosal paint propellants. Its new use as a clean fuel source is gaining attention and research, as it contains no sulfur or nitrogen compounds, has a very low toxicity, and is not corrosive to metals. It can be stored and transported as a liquid at low temperatures

A single-stage, liquid phase synthesis process for DME in a slurry phase reactor system is efficient and facilatates heat removal. The combination of methanol synthesis and methanol dehydration reversible reactions in a single step is thermodynamically more favorable. The liquid phase operation allows for better heat management and higher yields of DME.

The first pictured reaction shows the methanol synthesized from carbon dioxide and it is combined with the second pictured reaction into the last pictured reaction, in which the synthesized methanol is dehydrated to produce DME.

See here for the CiteULike with the reactions and here for another journal article about DME. In addition, the catalytic synthesis of methanol is covered in Ch.10 of Wade and DME itself is discussed in Ch.14.

The above reaction is an example of a Williamson synthesis of an ether. It is one the earlier steps in the reaction mechanism resulting in the octaethylene glycol derivative of 1,1,1,3,5,5,5-heptamethyltrisiloxane. Such an initial Williamson synthesis reaction had to be carried out so that later steps in the reaction—that is, ones involving material types not readily accessible—could successfully yield the derivative product. The resultant glycol derivative is an example of a defined surfactant. This particular journal article focused on the correlation between surfactant constituents and the effect on properties such as spreading performance.
The Williamson synthesis involves an SN2 reaction in which a halogen, sulfonyl, or sulfate group is replaced by an alkoxide ion, which can itself be prepared by a reaction of the alcohol with an active metal such as sodium or its hydride (i.e. NaH). The resultant alkoxide salt then reacts with the alkyl halide (must be primary) to produce an ether via the SN2 mechanism.
Other examples of Williamson synthesis of ethers can be found in this same reaction mechanism used to produce the surfactant.