Hajos-Parrish Ketone Research Articles

A unified total synthesis route to 18-trideuterated and/or 19-trideuterated testosterone, androstenedione and progesterone

A unified total synthesis route has been used to prepare 18- and 19-trideuterated testosterone, androstenedione and progesterone. The 18-trideuterated steroid synthetic method starts with the synthesis of 2-(methyl-d3)-1,3-cyclopentanedione from CD3I and 1,3-cyclopentanedione and is subsequently converted into the Hajos-Parrish ketone for synthesis of these trideuterated steroids. The 19-trideuterated steroid synthesis proceeds through non-deuterated Hajos-Parrish ketone with incorporation of the 19-methyl-d3 group from CD3I at a later stage of the same synthetic route. Utilization of CD3I at both the initial and later stages of the synthesis provides a route to 18,19-hexadeuterated steroids. The deuterated steroids are useful for studies of steroid biosynthesis and metabolism.

Synthesis of dydrogesterone by aromatization-dearomatization strategy

Dydrogesterone as an agonist of the progesterone receptor is an important and selective synthetic progesterone used for the treatment of a variety of conditions associated with progesterone deficiency including menstrual cycle regulation, infertility, and prevention of miscarriage. Its manufacturing process employing photochemical reactions remains a significant challenge. Herein we report the first total synthesis of dydrogesterone via a key 10α-substitution-selective dearomative cyclizationfree of photochemical protocols starting from Hajos-Parrish ketone. A gram-scale synthesis is also accomplished from readily available 9-hydroxy-4-androstene-3,17-dione through a novel aromatization-dearomatization strategy of ring A in steroid chemistry. Key synthetic features include a facile chemical aromatization of 9-hydroxy-4-androstene-3,17-dione, efficient ligand-controlled asymmetric dearomative cyclization to install the 10α-Me group, and an effective hydroxyl-directed hydrogenation of sterically congested tetrasubstituted olefin to establish the 8β-H,9β-H stereochemistry.

Assembling the Methanoindene Cage of Phragmalin-Type Natural Products.

Phragmalin-type limonoids are highly complex natural products based on an unusual octahydro-1H-2,4-methanoindene cage. The absence of feasible routes to sufficiently functionalized methanoindene cage building blocks impedes the total synthesis of these natural products. We have developed a short and robust route to methanoindene cage compounds from the Hajos-Parrish ketone (HPK). Several stereoselective modifications of the HPK provided a substrate that underwent aldol reaction as a key step for the cage formation.

Total Syntheses of Polyhydroxylated Steroids by an Unsaturation-Functionalization Strategy.

Highly oxygenated cardiotonic steroids such as ouabain possess a wide spectrum of biological functions and remain significant synthetic challenges. Herein we have applied an unsaturation-functionalization strategy and developed a synthetic method in addressing the C19-hydroxylation issue for efficient synthesis of polyhydroxylated steroids. An effective asymmetric dearomative cyclization allowed the construction of the C19-hydroxy unsaturated steroidal skeleton in only 4 steps from the Hajos-Parrish ketone ketal 7. A synthetic sequence featured C3-OH directed hydrogenation/epoxidation, m-CPBA triggered epoxidation/S N 2' nucleophilic substitution, Birch reduction of enone, and regioselective LiAlH4 reduction furnished the polyhydroxy functionalities on the steroid skeleton in high stereochemical control and efficiency, which has ultimately enabled thetotal synthesis of 19-hydroxysarmentogenin and ouabagenin in 18 and 19 overall steps, respectively. The syntheses of these polyhydroxylated steroids has offered synthetic versatility and practicality in search for new therapeutic agents.

Studies towards the Synthesis of (+)-Dictyoxetane.

The dolabellane-type diterpene dictyoxetane represents a significant challenge to synthetic organic chemistry. Methodology directed towards the total synthesis of naturally occurring (+)-dictyoxetane is reported. Catalytic asymmetric synthesis of the trans-hydrindane ring system is achieved through chemoselective deoxygenation of the Hajos-Parrish ketone. An alternative to the Garst-Spencer furan annulation is developed for the synthesis of a 2,5-dimethyl, tetrasubstituted furan, employing a tandem 5-exo-dig alcohol to alkyne cyclisation/aromatisation reaction as a key step. The (4+3) cycloaddition reaction of an oxyallyl cation with a tetrasubstituted furan is established on a cyclohexanone-derived model system, and a range of related (4+3) cycloadditions investigated on a homochiral, trans-hydrindane-fused furan, where regio- and diastereoselectivity is required for the natural product synthesis. In an alternative (4+2) Diels-Alder approach, a C2 -symmetric vinyl sulfoxide-based chiral ketene equivalent is used to prepare oxanorbornenes with the same oxygen bridge stereochemistry found in the 2,7-dioxatricyclo[4.2.1.03,8 ]nonane ring system of the natural product.

Construction of key building blocks towards the synthesis of cortistatins.

This work reports the construction of key building blocks towards the synthesis of cortistatins; a family of steroidal alkaloids. Cortistatin A, being a primary target due to its superior biological properties over other congeners, has been prepared by two different synthetic routes. Synthesis of the precursor to the heavily substituted A-ring starting from d-glucose and construction of the DE-ring junction employing a Hajos-Parrish ketone as a chiral pool have been demonstrated. Efforts are underway to assemble these key fragments and build towards the total synthesis of cortistatin A.

Heterocyclization and Spirocyclization Processes Based on Domino Reactions of N-Tosylhydrazones and Boronic Acids Involving Intramolecular Allylborylations of Nitriles.

Polycyclic molecules featuring all-carbon quaternary bridgehead centers were synthesized through domino cyclizations between N-tosylhydrazones and boronic acids. Variations of the general cascade have been applied for the preparation of 3-quinuclidinones and related alkaloid-like scaffolds through transannular heterocyclizations. Moreover, the employment of 3-cyanopropyl and 4-cyanobutylboronic acids and α,β-unsaturated N-tosylhydrazones led to spirocycles through unprecedented formal [n+1] cyclizations, including the stereoselective spirocyclization of the Hajos-Parrish ketone. The common feature of all the new reactions described is the creation of an all-carbon quaternary center by formation of two Csp3 -C bonds on the hydrazonic carbon atom. DFT-based calculations suggested the occurrence of cascade processes, which involve a diazo compound carboborylation followed by a 1,3-borotropic rearrangement on an intermediate allylboronic acid and a novel bora-aza-ene cyclization.

Enantioselective Total Synthesis of (+)-Wortmannin.

A concise and enantioselective total synthesis of the potent PI3K inhibitor (+)-wortmannin is described. A Pd-catalyzed cascade reaction was first developed to connect a synthon derived from Hajos-Parrish ketone to a furan moiety. The subsequent Friedel-Crafts alkylation of the β-position of a furan ring to an epoxide was optimized to establish the C10 quaternary center. (+)-Wortmannin was eventually accomplished by transformations following a late-stage oxidation of the furan allylic position. Kinome profiling and in vitro enzymatic assays were performed on 17-β-hydroxy-wortmannin and an epoxide analogue.

A Highly Active Polymer-Supported Catalyst for Asymmetric Robinson Annulations in Continuous Flow

The preparation through Robinson annulation of enantiopure building blocks with both academic and industrial relevance, such as the Wieland–Miescher and Hajos–Parrish ketones, has suffered from important drawbacks, such as the need for high catalyst loading or extremely long reaction times. Here we report a heterogenized organocatalyst based on Luo’s diamine for fast and broad-scope enantioselective Robinson annulation reactions. The polystyrene-supported diamine 19a enables the high-yield, highly enantioselective preparation of a wide range of chiral bicyclic enones under mild conditions, with reaction times as short as 60 min (batch) or residence times of 10 min (flow). In contrast with its homogeneous counterpart 19b, the catalytic resin 19a experiences a notable increase in catalytic activity with temperature in 2-MeTHF (a 10-fold decrease in reaction times without erosion in enantioselectivity is observed from room temperature to 55 °C). The scope of the transformation in batch mode has been illustrated with 14 examples, including examples only reported in poorly enantioenriched (22n) or in racemic form (22k). Enantiopure 22k has been used as the starting material for a straightforward formal synthesis of the antibiotic and antifeedant sesquiterpene (−)-isovelleral (24). The heterogenized catalyst 19a admits extended recycling (10 cycles) and has been used to develop the first asymmetric Robinson annulations in continuous flow. The potential of the flow process is illustrated by the large-scale preparation of the Wieland–Miescher ketone (65 mmol in 24 h of operation, TON of 117) and by a sequential flow experiment leading to a library of eight enantioenriched diketone compounds.

A total synthesis of (−)-hortonone C

A total synthesis of the cytotoxic terpenoid hortonone C was accomplished and its absolute stereochemistry confirmed. Intermediate (+)-4 was synthesized using either an asymmetric conjugate addition strategy, or by elaboration of the Hajos-Parrish ketone. Reduction of (+)-4 under dissolving-metal conditions and trapping the enolate intermediate served to control the cis-stereochemistry at the ring fusion and provide a silyl enol ether necessary for ring expansion. Comparison of optical rotation data confirmed that the absolute configuration of natural hortonone C is (6S,7S,10S).

Design and Synthesis of Non-peptide RGD Mimics for Evaluation of Their Utility as Anti-platelet Agents.

Arg-Gly-Asp (RGD) mimics were synthesized and their anti-platelet activity was evaluated. A concise method was developed for the synthesis of the target compounds from dehydroepiandrosterone and Wieland-Miescher and Hajos-Parrish ketones, which are suitable for readily available platform. Among the synthesized compounds, the perhydronaphthalene framework with a 3-(4-piperidinyl)propoxyl structure 3e possessed the highest anti-aggregative activity. The IC50 values of 3e were 0.91 mM (ADP initiation) and 0.54 mM (collagen initiation).

ChemInform Abstract: Synthesis and Applications of Hajos—Parrish Ketone Isomers.

Numerous natural products possess ring systems and functionality for which Hajos–Parrish ketone isomers with a transposed methyl group (termed “iso-Hajos–Parrish ketones”) would be of value. However, such building blocks have not been exploited to the same degree as the more typical Hajos–Parrish hydrindane. An efficient three-step synthesis of such materials was fueled by a simple method for the rapid preparation of highly functionalized cyclopentenones, several of which are new chemical entities that would be challenging to access through other approaches. Furthermore, one iso-Hajos–Parrish ketone was converted into two distinct natural product analogues and one natural product. As one indication of the value of these new building blocks, that latter target was obtained in 10 steps, having previously been accessed in 18 steps using the Hajos–Parrish ketone.

Synthesis and Applications of Hajos–Parrish Ketone Isomers

AbstractNumerous natural products possess ring systems and functionality for which Hajos–Parrish ketone isomers with a transposed methyl group (termed “iso‐Hajos–Parrish ketones”) would be of value. However, such building blocks have not been exploited to the same degree as the more typical Hajos–Parrish hydrindane. An efficient three‐step synthesis of such materials was fueled by a simple method for the rapid preparation of highly functionalized cyclopentenones, several of which are new chemical entities that would be challenging to access through other approaches. Furthermore, one iso‐Hajos–Parrish ketone was converted into two distinct natural product analogues and one natural product. As one indication of the value of these new building blocks, that latter target was obtained in 10 steps, having previously been accessed in 18 steps using the Hajos–Parrish ketone.

Synthesis and Applications of Hajos-Parrish Ketone Isomers.

Numerous natural products possess ring systems and functionality for which Hajos-Parrish ketone isomers with a transposed methyl group (termed "iso-Hajos-Parrish ketones") would be of value. However, such building blocks have not been exploited to the same degree as the more typical Hajos-Parrish hydrindane. An efficient three-step synthesis of such materials was fueled by a simple method for the rapid preparation of highly functionalized cyclopentenones, several of which are new chemical entities that would be challenging to access through other approaches. Furthermore, one iso-Hajos-Parrish ketone was converted into two distinct natural product analogues and one natural product. As one indication of the value of these new building blocks, that latter target was obtained in 10 steps, having previously been accessed in 18 steps using the Hajos-Parrish ketone.

Protecting-group-free total synthesis of aplykurodinone-1.

A concise, stereoselective, and protecting-group-free total synthesis of aplykurodinone-1 from Hajos-Parrish ketone was described. The synthetic approach features a sequence of aerobic allylic oxidation and elimination of alcohol 9. The key intermediate for this synthesis was formed by a stereoselective intramolecular radical cyclization.

A Practical Protocol for Asymmetric Synthesis of Wieland-Miescher and Hajos-Parrish Ketones Catalyzed by a Simple Chiral Primary Amine

This article describes a simple chiral primary amine catalyzed efficient and practical protocol for the large-scale synthesis of Wieland–Miescher and Hajos–Parrish ketones as well as their analogues­.

The A-CD analogue of 16β,17α-estriol is a potent and highly selective estrogen receptor β agonist

Selective estrogen receptor β (ERβ) agonists display neuroprotective properties in animal models and hold promise in the treatment of neurodegenerative diseases. In our quest to design, synthesize and evaluate potent and safe ERβ agonists, we focused on making an analogue of 16β,17α-estriol (16,17-epiestriol), a potent and one of the most ERβ selective endogenous estrogens reported. Herein we disclose the synthesis and in vitro evaluation of an analogue based on the recently introduced A-CD scaffold. A 14-step synthesis based on the Hajos–Parrish ketone resulted in the discovery of (1S,2S,3aS,5S,7aS)-5-(4-hydroxyphenyl)-7a-methyloctahydro-1H-indene-1,2-diol (15). This A-CD analogue of 16β,17α-estriol is a highly selective (500-fold) ERβ full agonist over ERα with a pEC50 of 7.7 at ERβ. Molecular modelling suggests that 15 turns around in the ligand-binding domain compared to estriol, thus the 7a-methyl occupies the α-face, which might explain the high selectivity.

A concise, enantiospecific, Hajos-Parrish ketone based model approach toward the tetracyclic core of complex shiartane-type nortriterpenoid natural products

A concise approach toward the tetracyclic (ABCD) core present in many complex shiartane-type bioactive nortriterpenoids has been conceptualized and executed from the readily available Hajos-Parrish ketone.

ChemInform Abstract: Asymmetric Synthesis of Wieland—Miescher and Hajos—Parrish Ketones Catalyzed by an Amino Acid Derived Chiral Primary Amine.

AbstractThe amine efficiently promotes the enantioselective formation of the title ketones and related compounds.

Asymmetric Synthesis of Wieland–Miescher and Hajos–Parrish Ketones Catalyzed by an Amino-Acid-Derived Chiral Primary Amine

This paper describes a simple chiral primary amine-catalyzed highly efficient and practical protocol for the synthesis of both Wieland-Miescher ketone and Hajos-Parrish ketone as well as their analogues. The reaction can be conducted in gram scale with 1% mol catalyst loading producing high enantioselectivity (up to 96% ee) and excellent yields (up to 98%). This procedure represents one of the most efficient methods for the synthesis of these versatile chiral building blocks.