Chemo-Enzymatic Strategy for the Efficient Synthesis of Steroidal Drugs with 10α-Methyl Group and a Side Chain at C17-Position from Biorenewable Phytosterols.

Steroidal pharmaceuticals with a 10α-methyl group or without the methyl group at C10-position are important medicines, but their synthesis is quite challenging, due to that the natural steroidal starting materials usually have a 10ß-methyl group which is difficult to be inverted to 10α-methyl group. In this study, 3-((1R,3aS,4S,7aR)-1-((S)-1-hydroxypropan-2-yl)-7a-methyl-5-oxooctahydro-1H-inden-4-yl) propanoic acid (HIP-IPA, 2e) was demonstrated as a valuable intermediate for the synthesis of this kind of active pharmaceutical ingredients (APIs) with a side chain at C17-position. Knockout of a ß-hydroxyacyl-CoA dehydrogenase gene and introduction of a sterol aldolase gene into the genetically modified strains of Mycobacterium fortuitum (ATCC 6841) resulted in strains N13Δhsd4AΩthl and N33Δhsd4AΩthl, respectively. Both strains transformed phytosterols into 2e. Compound 2e was produced in 62% isolated yield (25 g) using strain N13Δhsd4AΩthl, and further converted to (3S,3aS,9aS,9bS)-3-acetyl-3a,6-dimethyl-1,2,3,3a,4,5,8,9,9a,9b-decahydro-7H-cyclopenta[a]naphthalen-7-one, which is the key intermediate for the synthesis of dydrogesterone. This study not only overcomes a challenging synthetic problem by enabling an efficient synthesis of dydrogesterone-like steroidal APIs from phytosterols, the well-recognized cheap and readily available biobased raw materials, but also provides insights for redesigning the metabolic pathway of phytosterols to produce other new compounds of relevance to the steroidal pharmaceutical industry.

A citric acid cycle-deficient Escherichia coli as an efficient chassis for aerobic fermentations.

Tricarboxylic acid cycle (TCA cycle) plays an important role for aerobic growth of heterotrophic bacteria. Theoretically, eliminating TCA cycle would decrease carbon dissipation and facilitate chemicals biosynthesis. Here, we construct an E. coli strain without a functional TCA cycle that can serve as a versatile chassis for chemicals biosynthesis. We first use adaptive laboratory evolution to recover aerobic growth in minimal medium of TCA cycle-deficient E. coli. Inactivation of succinate dehydrogenase is a key event in the evolutionary trajectory. Supply of succinyl-CoA is identified as the growth limiting factor. By replacing endogenous succinyl-CoA dependent enzymes, we obtain an optimized TCA cycle-deficient E. coli strain. As a proof of concept, the strain is engineered for high-yield production of four separate products. This work enhances our understanding of the role of the TCA cycle in E. coli metabolism and demonstrates the advantages of using TCA cycle-deficient E. coli strain for biotechnological applications.

Feasibility study of using low-kilovoltage, prospective gating, high-pitch, dual-source computed tomography prior to transcatheter aortic valve replacement: analysis of image quality and radiation dose.

Background: Computed tomography (CT) scans before transcatheter aortic valve replacement (TAVR) are used to evaluate the aortic valve and guide the selection of appropriate valve stents. Accurate imaging evaluation can ensure the success rate of surgery while reducing the incidence of complications. Multiple studies have adopted a protocol of coronary artery, aortic valve, and total aortic scan, with the patients receiving higher radiation doses. The aim of this study was to evaluate the image quality, radiation dose, and diagnostic performance of dual-source computed tomography (DSCT) with high-pitch spiral scanning for TAVR. Methods: A total of 240 patients being evaluated for TAVR were continuously enrolled. Based on the differences in electrocardiography (ECG) gating and tube voltage, the patients were divided into 4 groups: group A, 70-kV prospective ECG gating, high-pitch helical; group B, 70-kV retrospective ECG gating; group C, 100-kV prospective ECG gating, high-pitch helical; and group D, 120-kV prospective ECG gating, high-pitch helical. Image quality was evaluated on a 4-point scale. The image signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated for objective evaluation. The radiation doses of all patients were recorded. The image quality and radiation dose of each group were compared. Results: There were no differences in age, body mass index (BMI), subjective image quality scores, CT values between the aorta and the coronary artery, or image CNR between the 4 groups. The mean radiation doses of groups A-D were 4.13±0.69, 4.79±0.58, 12.00±1.62, and 15.01±1.90 mSv, respectively. The mean radiation dose in group A (70-kV prospective ECG gating) decreased significantly (P<0.05). Conclusions: Using low-kilovoltage, high-pitch DSCT can provide comparable image quality for TAVR evaluation and significantly reduce the radiation dose.