Reductive biotransformation of diethyl beta-, gamma- and delta-oxoalkylphosphonates by cells of baker's yeast

Asymmetric Synthesis of β-Hydroxyphosphonates via a Chemoenzymatic Cascade

Chiral β-hydroxyphosphonates are essential building blocks for organophosphorus compounds. However, the asymmetric synthesis of these units remains a significant challenge. Herein, we describe a one-pot chemoenzymatic cascade process to access chiral β-hydroxyphosphonates, which combines photo-oxidative chemical reactions and bioreductions. The incorporation of photooxidation in the chemical reaction resulted in up to 92% yield and >99% enantiomeric excess (ee) of β-hydroxyphosphonates in the cascade. In addition, the scale-up of diethyl (S)-(2-hydroxy-2-phenylethyl)phosphonate demonstrates the potential application of this strategy.

Versatile Applications of Cyanobacteria in Biotechnology

Cyanobacteria are blue-green Gram-negative and photosynthetic bacteria which are seen as one of the most morphologically numerous groups of prokaryotes. Because of their ability to fix gaseous nitrogen and carbon dioxide to organic materials, they are known to play important roles in the universal nutrient cycle. Cyanobacteria has emerged as one of the promising resources to combat the issues of global warming, disease outbreaks, nutrition insecurity, energy crises as well as persistent daily human population increases. Cyanobacteria possess significant levels of macro and micronutrient substances which facilitate the versatile popularity to be utilized as human food and protein supplements in many countries such as Asia. Cyanobacteria has been employed as a complementary dietary constituent of feed for poultry and as vitamin and protein supplement in aquatic lives. They are effectively used to deal with numerous tasks in various fields of biotechnology, such as agricultural (including aquaculture), industrial (food and dairy products), environmental (pollution control), biofuel (bioenergy) and pharmaceutical biotechnology (such as antimicrobial, anti-inflammatory, immunosuppressant, anticoagulant and antitumor); recently, the growing interest of applying them as biocatalysts has been observed as well. Cyanobacteria are known to generate a numerous variety of bioactive compounds. However, the versatile potential applications of cyanobacteria in biotechnology could be their significant growth rate and survival in severe environmental conditions due to their distinct and unique metabolic pathways as well as active defensive mechanisms. In this review, we elaborated on the versatile cyanobacteria applications in different areas of biotechnology. We also emphasized the factors that could impede the implementation to cyanobacteria applications in biotechnology and the execution of strategies to enhance their effective applications.

Enantioselective vinylogous aldol reaction of acylphosphonates with 3-alkylidene oxindoles

A simple strategy for yielding chiral tertiary α-hydroxy phosphonates that integrates two highly biologically relevant scaffolds namely 3-alkylidene-2-oxindoles and phosphonates has been described. The hydrogen bonding ability of the bifunctional thiourea catalyst allows simultaneous dual activation of a vinylogous oxindole nucleophile and an acylphosphonate electrophile, affording hydroxyphosphonato-3-alkylidene-2-oxindoles as aldol adducts in high yields (up to 92%) with excellent stereocontrol (up to 99% ee).

Reductive activity of free and immobilized cells of cyanobacteria toward oxophosphonates-comparative study

This report, based on the previous studies, compares the reductive activity of different modes of following photobiocatalysts (on laboratory and preparative scale): Arthrospira maxima, Nostoc cf. muscorum and Nodularia sphaerocarpa, toward diethyl esters of 2-oxopropylphosphonate (1), 2-oxo-2-phenylethylphosphonate (2), and 2-oxobutylphosphonate (3). It was confirmed that immobilization in alginate matrix do not affect the activity and viability of the biocatalysts. Corresponding (S)-hydroxyphosphonates (1a-3a) were obtained with similar efficiency compared to the free-cell mode with the yield and of the optical purity e.e respectively (e.g., N. sphaerocarpa experiments): (1) yield: 21 %, e.e. 84 %; (2) yield 97 %, e.e. 97; (3) yield 21 %, e.e. 89 %. Scaling up the processes for the best biocatalyst, N. sphaerocarpa, indicated that the use of free-living cells of cyanobacteria is more effective (640 mg of substrate 2, 44 % of yield, 91 % of e.e.), compared to the column bioreactor packed with immobilized cells of this photobiocatalyst (384 mg of substrate 2, 38 % of yield, 86 % of e.e). In the case of free and immobilized cells of N. cf. muscorum, agitation of the medium was the crucial activity mediator. Shaking culture of free cells of N. cf. muscorum converted the diethyl 2-oxo-2-phenylethylphosphonate (2) with the yield of 43 % (99 % of e.e.) compared to 18 % (99 % of e.e., stationary culture). Immobilized cells of this cyanobacterium were also more active toward (2) under shaking conditions (28 % of yield, 99 % of e.e.) than free ones without agitation.

Enantiodifferentiation of alpha-hydroxyalkanephosphonic acids in 31P NMR with application of alpha-cyclodextrin as chiral discriminating agent

Alpha-cyclodextrin was shown to be convenient chemical shift reagent for determination of the enantiomeric composition of alpha-hydroxyphosphonic acids by means of 31P NMR. The developed methodology appeared to be reliable, repetitive, easy to perform and simple for interpretation. Enantiomeric discrimination in the 31P NMR spectra for 12 of 13 studied hydroxyphosphonates was achieved, with baseline separation of resonances obtained for eight compounds. In those cases, the chemical nonequivalence values ranged from 0.069 to 0.313 ppm. The studies showed that enantioselectivity is strongly influenced by the solution pD and the optimal condition was found at pD 2 or 10 depending on the guest structure. On the basis of the ROESY spectra the complexation modes of selected hydroxyphosphonates with alpha-cyclodextrin was postulated.