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Torsional steering as friend and foe: development of a synthetic route to the briarane diterpenoid stereotetrad.

ABSTRACT: Two synthetic routes to the briarane stereotetrad have been investigated. The first route employed a boron aldol reaction to establish the stereogenic all-carbon quaternary carbon (C1). In this case, it was found that torsional steering in the transition state led to the formation of the undesired configuration at this position. The second route makes use of a highly diastereoselective acetylide conjugate addition/?-ketoester alkylation sequence to construct the vicinal C1 and C10 stereocenters with the correct relative configuration. Originally, it was proposed that torsional steering in the transition state for the ketoester alkylation step was the primary factor responsible for generating the major product. DFT calculations reveal that while torsional steering does play a role, larger conformational factors must also be considered. These calculations also reveal that an unusual C-H?(alkyne) interaction may contribute to lowering the energy of one transition state that leads to the observed stereoisomer. Ultimately, this strategy leads to a concise synthesis (under 10 steps) of the stereotetrad core common to the briarane diterpenoids.

SUBMITTER: Moon NG

PROVIDER: S-EPMC5330299 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Torsional steering as friend and foe: development of a synthetic route to the briarane diterpenoid stereotetrad.

Moon Nicholas G NG Harned Andrew M AM

Organic & biomolecular chemistry 20170201 8

Two synthetic routes to the briarane stereotetrad have been investigated. The first route employed a boron aldol reaction to establish the stereogenic all-carbon quaternary carbon (C1). In this case, it was found that torsional steering in the transition state led to the formation of the undesired configuration at this position. The second route makes use of a highly diastereoselective acetylide conjugate addition/β-ketoester alkylation sequence to construct the vicinal C1 and C10 stereocenters ...[more]

PMID: 28169385

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Project description:BackgroundA higher chemotherapy completion rate is associated with better outcomes including treatment efficacy and overall survival. Exercise may have the potential to improve relative dose intensity (RDI) by reducing the frequency and severity of chemotherapy-related toxicities. We examined the association between exercise adherence and RDI and possible clinical- and health-related fitness predictors of RDI.MethodsChemotherapy records were extracted from the electronic medical record for patients enrolled in the ENACT trial (n = 105). Chemotherapy completion was assessed using average RDI. A threshold of 85% was established for "high" versus "low" RDI. Logistic regression analyses were used to estimate the associations between the clinical- and health-related fitness predictors of RDI.ResultsPatients with breast cancer (BC) had a significantly higher average RDI (89.8% ± 17.6%) compared with gastrointestinal cancer (GI) (76.8% ± 20.9%, p = 0.004) and pancreatic cancer (PC) (65.2% ± 20.1%, p < 0.001). Only 25% of BC patents required a dose reduction compared to 56.3% of GI and 86.4% of PC patients. Cancer site was significantly associated with RDI. Compared with BC, patients with GI (β = -0.12, p = 0.03) and PC (β = -0.22, p = 0.006) achieved significantly lower RDI. Every 2.72 unit increase in overall exercise adherence led to a significant 7% decrease in RDI (p = 0.001) in GI patients. Metastatic GI patients had a 15% RDI increase for every 2.72 unit increase in exercise adherence (p = 0.04).ConclusionExercise is a supportive therapy that has potential to enhance chemotherapy tolerance and completion. The relationship between exercise adherence and RDI is influenced by factor such as cancer site and treatment type. Special attention must be paid to how exercise is prescribed to ensure that exercise adherence does not negatively affect RDI. Cancer site, exercise dosage, and multimodal interventions to address toxicities are key areas identified for future research.

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Torsional steering as friend and foe: development of a synthetic route to the briarane diterpenoid stereotetrad.

Publications

Torsional steering as friend and foe: development of a synthetic route to the briarane diterpenoid stereotetrad.

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