Multifunctional biocatalyst for conjugate reduction and reductive amination.

Chiral amine diastereomers are ubiquitous in pharmaceuticals and agrochemicals1, yet their preparation often relies on low-efficiency multi-step synthesis2. These valuable compounds must be manufactured asymmetrically, as their biochemical properties can differ based on the chirality of the molecule. Herein we characterize a multifunctional biocatalyst for amine synthesis, which operates using a mechanism that is, to our knowledge, previously unreported. This enzyme (EneIRED), identified within a metagenomic imine reductase (IRED) collection3 and originating from an unclassified Pseudomonas species, possesses an unusual active site architecture that facilitates amine-activated conjugate alkene reduction followed by reductive amination. This enzyme can couple a broad selection of α,ß-unsaturated carbonyls with amines for the efficient preparation of chiral amine diastereomers bearing up to three stereocentres. Mechanistic and structural studies have been carried out to delineate the order of individual steps catalysed by EneIRED, which have led to a proposal for the overall catalytic cycle. This work shows that the IRED family can serve as a platform for facilitating the discovery of further enzymatic activities for application in synthetic biology and organic synthesis.

Multifunctional Biocatalysts for Organic Synthesis.

Biocatalysis is becoming an indispensable tool in organic synthesis due to high enzymatic catalytic efficiency as well as exquisite chemo- and stereoselectivity. Some biocatalysts display great promiscuity including a broad substrate scope as well as the ability to catalyze more than one type of transformation. These promiscuous activities have been applied individually to efficiently access numerous valuable target molecules. However, systems in which enzymes possessing multiple different catalytic activities are applied in the synthesis are less well developed. Such multifunctional biocatalysts (MFBs) would simplify chemical synthesis by reducing the number of operational steps and enzyme count, as well as simplifying the sequence space that needs to be engineered to develop an efficient biocatalyst. In this Perspective, we highlight recently reported MFBs focusing on their synthetic utility and mechanism. We also offer insight into their origin as well as comment on potential strategies for their discovery and engineering.

Synthesis of Stereoenriched Piperidines via Chemo-Enzymatic Dearomatization of Activated Pyridines.

The development of efficient and sustainable methods for the synthesis of nitrogen heterocycles is an important goal for the chemical industry. In particular, substituted chiral piperidines are prominent targets due to their prevalence in medicinally relevant compounds and their precursors. A potential biocatalytic approach to the synthesis of this privileged scaffold would be the asymmetric dearomatization of readily assembled activated pyridines. However, nature is yet to yield a suitable biocatalyst specifically for this reaction. Here, by combining chemical synthesis and biocatalysis, we present a general chemo-enzymatic approach for the asymmetric dearomatization of activated pyridines for the preparation of substituted piperidines with precise stereochemistry. The key step involves a stereoselective one-pot amine oxidase/ene imine reductase cascade to convert N-substituted tetrahydropyridines to stereo-defined 3- and 3,4-substituted piperidines. This chemo-enzymatic approach has proved useful for key transformations in the syntheses of antipsychotic drugs Preclamol and OSU-6162, as well as for the preparation of two important intermediates in synthetic routes of the ovarian cancer monotherapeutic Niraparib.

New Trends and Future Opportunities in the Enzymatic Formation of C-C, C-N, and C-O bonds.

Organic chemistry provides society with fundamental products we use daily. Concerns about the impact that the chemical industry has over the environment is propelling major changes in the way we manufacture chemicals. Biocatalysis offers an alternative to other synthetic approaches as it employs enzymes, Nature's catalysts, to carry out chemical transformations. Enzymes are biodegradable, come from renewable sources, operate under mild reaction conditions, and display high selectivities in the processes they catalyse. As a highly multidisciplinary field, biocatalysis benefits from advances in different areas, and developments in the fields of molecular biology, bioinformatics, and chemical engineering have accelerated the extension of the range of available transformations (E. L. Bell et al., Nat. Rev. Meth. Prim. 2021, 1, 1-21). Recently, we surveyed advances in the expansion of the scope of biocatalysis via enzyme discovery and protein engineering (J. R. Marshall et al., Tetrahedron 2021, 82, 131926). Herein, we focus on novel enzymes currently available to the broad synthetic community for the construction of new C-C, C-N and C-O bonds, with the purpose of providing the non-specialist with new and alternative tools for chiral and sustainable chemical synthesis.

Synthesis of Pharmaceutically Relevant 2-Aminotetralin and 3-Aminochroman Derivatives via Enzymatic Reductive Amination.

2-Aminotetralin and 3-aminochroman derivatives are key structural motifs present in a wide range of pharmaceutically important molecules. Herein, we report an effective biocatalytic approach towards these molecules through the enantioselective reductive coupling of 2-tetralones and 3-chromanones with a diverse range of primary amine partners. Metagenomic imine reductases (IREDs) were employed as the biocatalysts, obtaining high yields and enantiocomplementary selectivity for >15 examples at preparative scale, including the precursors to Ebalzotan, Robalzotan, Alnespirone and 5-OH-DPAT. We also present a convergent chemo-enzymatic total synthesis of the Parkinson's disease therapy Rotigotine in 63 % overall yield and 92 % ee.

Asymmetric Synthesis of N-Substituted α-Amino Esters from α-Ketoesters via Imine Reductase-Catalyzed Reductive Amination.

N-Substituted α-amino esters are widely used as chiral intermediates in a range of pharmaceuticals. Here we report the enantioselective biocatalyic synthesis of N-substituted α-amino esters through the direct reductive coupling of α-ketoesters and amines employing sequence diverse metagenomic imine reductases (IREDs). Both enantiomers of N-substituted α-amino esters were obtained with high conversion and excellent enantioselectivity under mild reaction conditions. In addition >20 different preparative scale transformations were performed highlighting the scalability of this system.

Development of Continuous Flow Systems to Access Secondary Amines Through Previously Incompatible Biocatalytic Cascades*.

A key aim of biocatalysis is to mimic the ability of eukaryotic cells to carry out multistep cascades in a controlled and selective way. As biocatalytic cascades get more complex, reactions become unattainable under typical batch conditions. Here a number of continuous flow systems were used to overcome batch incompatibility, thus allowing for successful biocatalytic cascades. As proof-of-principle, reactive carbonyl intermediates were generated in situ using alcohol oxidases, then passed directly to a series of packed-bed modules containing different aminating biocatalysts which accordingly produced a range of structurally distinct amines. The method was expanded to employ a batch incompatible sequential amination cascade via an oxidase/transaminase/imine reductase sequence, introducing different amine reagents at each step without cross-reactivity. The combined approaches allowed for the biocatalytic synthesis of the natural product 4O-methylnorbelladine.

One-Pot Biocatalytic Cascade Reduction of Cyclic Enimines for the Preparation of Diastereomerically Enriched N-Heterocycles.

Ene-reductases (EREDs) catalyze the reduction of electron-deficient C═C bonds. Herein, we report the first example of ERED-catalyzed net reduction of C═C bonds of enimines (α,ß-unsaturated imines). Preliminary studies suggest their hydrolyzed ring-open ω-amino enones are the likely substrates for this step. When combined with imine reductase (IRED)-mediated C═N reduction, the result is an efficient telescoped sequence for the preparation of diastereomerically enriched 2-substituted saturated amine heterocycles.

Chemoenzymatic Synthesis of Substituted Azepanes by Sequential Biocatalytic Reduction and Organolithium-Mediated Rearrangement.

Enantioenriched 2-aryl azepanes and 2-arylbenzazepines were generated biocatalytically by asymmetric reductive amination using imine reductases or by deracemization using monoamine oxidases. The amines were converted to the corresponding N'-aryl ureas, which rearranged on treatment with base with stereospecific transfer of the aryl substituent to the 2-position of the heterocycle via a configurationally stable benzyllithium intermediate. The products are previously inaccessible enantioenriched 2,2-disubstituted azepanes and benzazepines.

Laparoscopic Lavage in the Management of Hinchey Grade III Diverticulitis: A Systematic Review.

OBJECTIVE: To compare the outcomes of laparoscopic lavage and sigmoid resection in perforated diverticulitis with purulent peritonitis. BACKGROUND: Peritonitis secondary to perforated diverticulitis has conventionally been managed by resection and stoma formation. Case series have suggested that patients can be safely managed with laparoscopic lavage, resulting in reduced mortality and stoma formation. Recently, 3 randomized controlled trials have published contradictory conclusions. METHODS: MEDLINE from 1946 to present, Cochrane Database of Systematic Reviews, and Cochrane database of Registered clinical trials and EMBASE (all via OVID) were searched using the terms "laparoscopy" AND ("primary resection" OR "Hartmann procedure", OR "sigmoidectomy"), AND "Diverticulitis", AND "Peritonitis" AND "therapeutic irrigation" or "lavage" AND randomized controlled trial and any derivatives of those terms. We included all randomized controlled trials. Data were extracted from each study using a purpose-designed template. Statistical analysis was undertaken using Revman 5. RESULTS: Three randomized controlled trials were identified from 48 potential studies. The analysis included 307 patients of whom 159 underwent laparoscopic lavage. Overall, the rate of reintervention within 30 days postoperatively was 45/159 (28.3%) in the lavage group and 13/148 (8.8%) in the resection group (relative risk 3.01, 95% confidence interval 1.15-7.90). There was no significant difference in Intensive Care Unit admissions, 30 and 90-day mortality, or stoma rates at 12 months. CONCLUSION: Laparoscopic lavage used in the management of Hinchey grade III diverticulitis leads to more reinterventions within 30 days postoperatively, but does not increase the 30 or 90-day mortality rates compared with sigmoid resection.

Validation of the Kattan Nomogram for Prostate Cancer Recurrence After Radical Prostatectomy.

BACKGROUND: The Kattan postoperative radical prostatectomy (RP) nomogram is used to predict biochemical recurrence-free progression (BCRFP) after RP. However, external validation among contemporary patients using modern outcome definitions is limited. METHODS: A total of 1,931 patients who underwent RP at Roswell Park Cancer Institute (RPCI) between 1993 and 2014 (median follow-up, 47 months; range, 0-244 months) were assessed for NCCN-defined biochemical failure (BF) and RPCI-defined treatment failure (TF). Actual rates of biochemical failure-free survival (BFS; defined as 1 - BF) and treatment failure-free survival (TFS; defined as 1 - TF) were compared with Kattan BCRFP nomogram predictions. RESULTS: The Kattan BCRFP nomogram predictions at 5 and 10 years were predictive of BFS (area under the receiver operating characteristic curve [AUC], 0.772) and TFS (AUC, 0.774). The Kattan BCRFP nomogram tended to underestimate BFS and TFS compared with actual outcomes. The Kattan 5-year BCRFP predictions consistently overestimated actual 5-year BFS outcomes among subgroups of high- and intermediate-risk patients with at least 5-year outcomes. CONCLUSIONS: The Kattan BCRFP nomogram is a robust predictor of NCCN-defined BF in a large sample of patients with RP with substantial follow-up and modern, standardized failure definitions.

Impact of devascularization and tissue procurement on cell number and RNA integrity in prostatectomy tissue.

BACKGROUND: Minimizing the time between tissue devascularization in robot-assisted laparoscopic radical prostatectomy (RALP) and tissue procurement should produce the highest quality tissue for research study. This study examines the relationship between intra-operative time and two indicators of tissue integrity: number of epithelial cells per gram of tissue and RNA integrity numbers (RINs). The study also compares the RIN values of tissue obtained intra-operatively by biopsy, before and after devascularization, to those from RALP specimen tissue, obtained through the routine research tissue procurement process. METHODS: Prostate tissues from two series of patients were analyzed. In the first, tissue from 18 patients undergoing RALP was analyzed for number of epithelial cells per gram of tissue. In the second, RIN values of tissue from 46 patients involved in a clinical study were analyzed. RIN values were assessed from RALP specimen tissue as well as tissue removed intra-operatively by biopsy, before and after devascularization. RESULTS: Time from RALP to tissue procurement was not significantly associated with number of epithelial cells per gram of tissue or with RIN values. RINs of biopsy tissue obtained intra-operatively before and after devascularization were similar. However, the RIN values of tissue from RALP specimens were significantly higher than those of biopsy tissue obtained either before or after devascularization. CONCLUSIONS: Tissue quality, defined by number of epithelial cells or RIN values, was not affected by time between devascularization and procurement. Obtaining tissue from intra-operative biopsies, either before or after devascularization, is not necessary and actually produced lower RINs than found in tissue from RALP specimens, obtained through the routine research tissue procurement process.

Intake of vitamins A, C, and E and folate and the risk of ovarian cancer in a pooled analysis of 10 cohort studies.

PURPOSE: Vitamins A, C, and E and folate have anticarcinogenic properties and thus might protect against cancer. Few known modifiable risk factors for ovarian cancer exist. We examined the associations between dietary and total (food and supplemental) vitamin intake and the risk of invasive epithelial ovarian cancer. METHODS: The primary data from 10 prospective cohort studies in North America and Europe were analyzed. Vitamin intakes were estimated from validated food frequency questionnaires in each study. Study-specific relative risks (RRs) were estimated using the Cox proportional hazards model and then combined using a random-effects model. RESULTS: Among 501,857 women, 1,973 cases of ovarian cancer occurred over a median follow-up period of 7-16 years across studies. Dietary and total intakes of each vitamin were not significantly associated with ovarian cancer risk. The pooled multivariate RRs [95% confidence intervals (CIs)] for incremental increases in total intake of each vitamin were 1.02 (0.97-1.07) for vitamin A (increment: 1,300 mcg/day), 1.01 (0.99-1.04) for vitamin C (400 mg/day), 1.02 (0.97-1.06) for vitamin E (130 mg/day), and 1.01 (0.96-1.07) for folate (250 mcg/day). Multivitamin use (vs. nonuse) was not associated with ovarian cancer risk (pooled multivariate RR = 1.00, 95% CI 0.89-1.12). Associations did not vary substantially by study, or by subgroups of the population. Greater vitamin intakes were associated with modestly higher risks of endometrioid tumors (n = 156 cases), but not with other histological types. CONCLUSION: These results suggest that consumption of vitamins A, C, and E and folate during adulthood does not play a major role in ovarian cancer risk.

Automated tobacco assessment and cessation support for cancer patients.

BACKGROUND: Tobacco assessment and cessation support are not routinely included in cancer care. An automated tobacco assessment and cessation program was developed to increase the delivery of tobacco cessation support for cancer patients. METHODS: A structured tobacco assessment was incorporated into the electronic health record at Roswell Park Cancer Institute to identify tobacco use in cancer patients at diagnosis and during follow-up. All patients who reported tobacco use within the past 30 days were automatically referred to a dedicated cessation program that provided cessation counseling. Data were analyzed for referral accuracy and interest in cessation support. RESULTS: Between October 2010 and December 2012, 11,868 patients were screened for tobacco use, and 2765 were identified as tobacco users and were referred to the cessation service. In referred patients, 1381 of those patients received only a mailed invitation to contact the cessation service, and 1384 received a mailing as well as telephone contact attempts from the cessation service. In the 1126 (81.4%) patients contacted by telephone, 51 (4.5%) reported no tobacco use within the past 30 days, 35 (3.1%) were medically unable to participate, and 30 (2.7%) declined participation. Of the 1381 patients who received only a mailed invitation, 16 (1.2%) contacted the cessation program for assistance. Three questions at initial consult and follow-up generated over 98% of referrals. Tobacco assessment frequency every 4 weeks delayed referral in < 1% of patients. CONCLUSIONS: An automated electronic health record-based tobacco assessment and cessation referral program can identify substantial numbers of smokers who are receptive to enrollment in a cessation support service.

Smoking at diagnosis and survival in cancer patients.

The effect of smoking on survival in cancer patients is limited by the lack of structured prospective assessments of smoking at diagnosis. To assess the effect of smoking at diagnosis on survival, structured smoking assessments were obtained in a cohort of 5,185 cancer patients within 30 days of a cancer diagnosis between 1982 and 1998. Hazard ratios (HRs) or odds ratios were generated to analyze the effects of smoking at diagnosis on overall mortality (OM) and disease-specific mortality (DSM) in a patient cohort from 13 disease sites containing at least 100 patients in each disease site. With a minimum of 12 years of follow-up, current smoking increased OM risk versus recent quit (HR 1.17), former (HR 1.29) and never smokers (HR 1.38) in the overall cohort. Current smoking increased DSM risk versus former (HR 1.23) and never smokers (HR 1.18). In disease sites with proportionately large (>20%) recent quit cohorts (lung and head/neck), current smoking increased OM and DSM risks as compared with recent quit. Current smoking increased mortality risks in lung, head/neck, prostate and leukemia in men and breast, ovary, uterus and melanoma in women. Current smoking was not associated with any survival benefit in any disease site. Data using prospective structured smoking assessments demonstrate that current smoking increased long-term OM and DSM. Standardized smoking assessment at diagnosis is an important variable for evaluating outcomes in cancer patients.

Accuracy of self-reported tobacco use in newly diagnosed cancer patients.

PURPOSE: Accurate identification of tobacco use is critical to implement evidence-based cessation treatments in cancer patients. The purpose of this study is to evaluate the accuracy of self-reported tobacco use in newly diagnosed cancer patients. METHODS: Tobacco use questionnaires and blood samples were collected from 233 newly diagnosed cancer patients (77 lung, 77 breast, and 79 prostate cancer). Blood was analyzed for cotinine levels using a commercially available enzyme-linked immunosorbent assay. Patients with cotinine measurements exceeding 10 ng/mL were categorized as current smokers. Smoking status based upon cotinine levels was contrasted with self-report in current smokers, recent quitters (1 or less year since quit), non-recent quitters (>1 year since quit), and never smokers. Multivariate analyses were used to identify potential predictors of discordance between self-reported and biochemically confirmed smoking. RESULTS: Cotinine confirmed 100 % accuracy in self-reporting of current and never smokers. Discordance in cotinine and smoking status was observed in 26 patients (15.0 %) reporting former tobacco use. Discordance in self-reported smoking was 12 times higher in recent (35.4 %) as compared with non-recent quitters (2.8 %). Combining disease site, pack-year history, and employment status predicted misrepresentation of tobacco use in 82.4 % of recent quitters. CONCLUSIONS: Self-reported tobacco use may not accurately assess smoking status in newly diagnosed cancer patients. Patients who claim to have recently stopped smoking within the year prior to a cancer diagnosis and lung cancer patients may have a higher propensity to misrepresent tobacco use and may benefit from biochemical confirmation.

Organ-specific exposure and response to sulforaphane, a key chemopreventive ingredient in broccoli: implications for cancer prevention.

Naturally occurring sulforaphane (SF) has been extensively studied for cancer prevention. However, little is known as to which organs may be most affected by this agent, which impedes its further development. In the present study, SF was administered to rats orally either in a single dose or once daily for 7 d. Tissue distribution of SF was measured by a HPLC-based method. Glutathione S-transferase (GST) and NAD(P)H:quinone oxidoreductase 1 (NQO1), two well-known cytoprotective phase 2 enzymes, were measured using biochemical assays to assess tissue response to SF. SF was delivered to different organs in vastly different concentrations. Tissue uptake of SF was the greatest in the stomach, declining rapidly in the descending gastro-intestinal tract. SF was rapidly eliminated through urinary excretion, and urinary concentrations of SF equivalents were 2-4 orders of magnitude higher than those of plasma. Indeed, tissue uptake level of SF in the bladder was second only to that in the stomach. Tissue levels of SF in the colon, prostate and several other organs were very low, compared to those in the bladder and stomach. Moreover, induction levels of GST and NQO1 varied by 3- to 6-fold among the organs of SF-treated rats, though not strictly correlated with tissue exposure to SF. Thus, there is profound organ specificity in tissue exposure and response to dietary SF, suggesting that the potential chemopreventive benefit of dietary SF may differ significantly among organs. These findings may provide a basis for prioritising organs for further chemopreventive study of SF.

Diet and prostate cancer prevention.

PURPOSE: To evaluate the present human-based evidence that diet is related to the risk and outcome of prostate cancer. METHODS: Review of major case-control and cohort studies, and experimental trials evaluating the effect of diet or dietary constituents on the risk of prostate cancer. RESULTS: Although non-experimental studies have suggested several dimensions of diet and several dietary components as related to risk and outcome of prostate cancer, the results of these studies are inconsistent. There is limited evidence that a diet that emphasizes plant products is associated with diminished risk of prostate cancer and of aggressive prostate cancer. CONCLUSION: The non-experimental epidemiologic evidence that has now accrued justifies trials of dietary intervention for those at elevated risk of prostate cancer.