ABSTRACT
A new synthetic approach has been developed for the preparation of 7-deoxypancratistatin analogues bearing a syn-(4aS,10bS)-phenanthridone ring junction. A one-pot tandem process involving a substrate-directed Overman rearrangement and ring closing metathesis reaction was developed for the stereoselective synthesis of a carbocyclic allylic trichloroacetamide. Conversion to a 6-bromopiperonyl amide, followed by a Heck reaction generated a homoallylic alcohol and completed the syn-(4aS,10bS)-phenanthridone carbon skeleton. Stereoselective epoxidation and dihydroxylation of the syn-(4aS,10bS)-phenanthridone framework was then investigated leading to the preparation of new analogues of 7-deoxypancratistatin.
Subject(s)
Amides/chemical synthesis , Phenanthrenes/chemistry , Epoxy Compounds/chemistry , Models, Molecular , Molecular Structure , StereoisomerismABSTRACT
OBJECTIVES: To determine the degree of conversion (DC) and Knoop microhardness (KHN) of resin-based composites (RBCs) containing trimethylbenzoyl-diphenylphosphine oxide (TPO) cured by polywave or monowave LED light-curing units (LCUs). METHODS: Three groups (each n = 5) of Tetric EvoCeram (Ivoclar Vivadent), Vit-l-escence (Ultradent) and Herculite XRV Ultra (Kerr) were prepared in Teflon moulds (5mm in diameter and 2mm thick) and cured with polywave Bluephase(®) G2 (Ivoclar Vivadent), polywave Valo (Ultradent) or monowave Bluephase(®) (Ivoclar Vivadent; control) resulting in 9 groups. DC and KHN were determined using micro-Raman spectroscopy and Knoop microhardness, respectively. High-performance liquid chromatography and nuclear magnetic resonance spectroscopy were used to confirm the presence or absence of TPO in the three uncured materials. Data were statistically analysed using two-way and one-way ANOVA and DC and KHN were correlated using Pearson's correlation (α = 0.05). RESULTS: TPO was confirmed in Tetric EvoCeram and Vit-l-escence but not in Herculite XRV Ultra. All three LCUs produced comparable KHN for Tetric EvoCeram and Herculite XRV Ultra (p > 0.05). Both polywave LCUs resulted in significantly higher KHN for Vit-l-escence and higher DC in Tetric EvoCeram and Vit-l-escence than the monowave Bluephase(®) (p < 0.05). Conversely, Bluephase(®) showed higher DC than the two polywave LCUs in Herculite XRV Ultra (p < 0.05). Pearson's correlation coefficient was r = 0.818. CONCLUSIONS: Polywave LED LCUs improved monomer to polymer conversion and KHN in the two TPO-containing RBCs, but not in Herculite XRV Ultra. DC and KHN were linearly correlated in all three RBCs. Vit-l-escence showed the highest DC and KHN of the three materials tested. CLINICAL SIGNIFICANCE: The use of polywave LEDs significantly improves both the DC and KHN of materials which contain TPO. This should be taken into account when curing bleached shades of RBCs even if the manufacturers do not indicate the presence of TPO in their materials.
Subject(s)
Composite Resins/chemistry , Curing Lights, Dental/classification , Dental Materials/chemistry , Phosphines/chemistry , Bisphenol A-Glycidyl Methacrylate/chemistry , Camphor/analogs & derivatives , Camphor/chemistry , Chromatography, High Pressure Liquid , Composite Resins/radiation effects , Dental Materials/radiation effects , Hardness , Humans , Magnetic Resonance Spectroscopy , Materials Testing , Methacrylates/chemistry , Microspectrophotometry , Photoinitiators, Dental/chemistry , Polyethylene Glycols/chemistry , Polymerization , Polymethacrylic Acids/chemistry , Polyurethanes/chemistry , Resin Cements/chemistry , Spectrum Analysis, RamanABSTRACT
A stereoselective synthesis of (+)-physoperuvine, a tropane alkaloid from Physalis peruviana Linne has been developed using a one-pot tandem aza-Claisen rearrangement and ring closing metathesis reaction to form the key amino-substituted cycloheptene ring.
Subject(s)
Alkaloids/chemical synthesis , Tropanes/chemical synthesis , Alkaloids/chemistry , Cyclization , Molecular Structure , Physalis/chemistry , Stereoisomerism , Tropanes/chemistryABSTRACT
A one-pot tandem palladium(II)-catalyzed aza-Claisen rearrangement and ring closing metathesis process has been developed for the efficient synthesis of cyclic allylic trichloroacetamides. The use of chiral Pd(II) catalysts such as (S)-COP-Cl during the rearrangement stage results in the preparation of these compounds in excellent yields and in high enantiomeric excess.
ABSTRACT
The use of a non-coordinating solvent for the aza-Claisen rearrangement of delta,epsilon-disubstituted acetimidates switches on a substrate directing effect that gives excellent stereoselectivity.
