Efficient Biosynthesis of (S)-1-chloro-2-heptanol Catalyzed by a Newly Isolated Fungi Curvularia hominis B-36

(S)-1-chloro-2-heptanol is an enantiopure chemical of great value that can synthesize Treprostinil for treating primary pulmonary hypertension. In this work, a new strain B-36, capable of asymmetric reduction of 1-chloro-2-heptanone to (S)-1-chloro-2-heptanol, was screened and identified as Curvularia hominis B-36 (CCTCC M 2017654) based on the morphological and internally transcribed spacer (ITS) sequence. The reductive capacity of Curvularia hominis B-36 was investigated as a whole-cell biocatalyst in the bioreduction, and the excellent yield (97.2%) and enantiomeric excess (ee) value (99.9%) were achieved under the optimal conditions as follows: 75 mM 1-chloro-2-heptanone, K2HPO4-KH2PO4 (100 mM, pH 6.0), 50 g L−1 resting cells (dry cell weight; DCW), 15% (v/v) isopropanol as co-substrate, 200 rpm, 30 °C, 20 h. The scaled-up biocatalytic process was accomplished at a bioreactor in a 1.5 L working volume, showing superb yield (~97%) and selectivity (99.9%). The product (S)-1-chloro-2-heptanol was purified and characterized by NMR. Curvularia hominis B-36 is a novel catalyst and the asymmetric synthesis route is benign and eco-friendly.

Study of the Pauson-Khand reaction in flow over alkynylphenyl vinyl ethers: towards the synthesis of tricyclic multisubstituted benzofurans

The use of flow methodology allows the use of alkynylphenyl vinyl ethers (benzo-fused 1,7 enynes) as substrates for the intramolecular Pauson-Khand reaction (PKr). Forced temperature and pressure conditions during a short reaction time minimize the substrate decomposition allowing the formation of the PK adduct. Substrates substituted at the internal position of the double bond and with internal triple bonds give better yields. The resulting products are cyclopentabenzofuranones present in diverse natural products and drugs that can be further functionalised.

Flow Chemistry for Cycloaddition Reactions

Continuous flow reactors form part of a rapidly growing research area that has changed the way synthetic chemistry is performed not only in academia but also at the industrial level. This Review highlights the most recent advances in cycloaddition reactions performed in flow systems. Cycloadditions are atom-efficient transformations for the synthesis of carbo- and heterocycles, involved in the construction of challenging skeletons of complex molecules. The main advantages of translating these processes into flow include using intensified conditions, safer handling of hazardous reagents and gases, easy tuning of reaction conditions, and straightforward scaling up. These benefits are especially important in cycloadditions such as the copper(I)-catalyzed azide alkyne cycloaddition (CuAAC), Diels-Alder reaction, ozonolysis and [2+2] photocycloadditions. Some of these transformations are key reactions in the industrial synthesis of pharmaceuticals.

Pauson-Khand reaction of fluorinated compounds

The Pauson-Khand reaction (PKR) is one of the key methods for the construction of cyclopentenone derivatives, which can in turn undergo diverse chemical transformations to yield more complex biologically active molecules. Despite the increasing availability of fluorinated building blocks and methodologies to incorporate fluorine in compounds with biological interest, there have been few significant advances focused on the fluoro-Pauson-Khand reaction, both in the inter- and intramolecular versions. Furthermore, the use of vinyl fluorides as olefinic counterparts had been completely overlooked. In this review, we collect the advances both on the stoichiometric and catalytic intermolecular and intramolecular fluoro-Pauson-Khand reaction, with special attention to the PKR of enynes containing a fluoride moiety.