Enantioselective dihydroxylation of xanthorrhizol from Curcuma xanthorrhiza via biotransformation using Aspergillus Niger

Biotransformation is acknowledged as one of the green chemistry methods to synthesis various analogues for further valorization of natural product compounds chemistry and bioactivities. It has huge advantage over chemical synthesis due to its cost-efficiency and higher selectivity. In this work, a xanthorrhizol derivatives, namely (7 R,10S)-10,11-dihydro-10,11-dihydroxyxanthorrhizol was produced in 60% yield from the biotransformation process utilizing A. niger. The structure of the compound was established by extensive spectroscopic methods and comparison with literature data. This biotransformation successfully afforded enantioselective dihydroxylation reaction via green chemistry route. This is the first report on both biotransformation of xanthorrhizol and utilization of A. niger as its biocatalyst.

Metal-Catalyst-Free One-Pot Aqueous Synthesis of trans-1,2-Diols from Electron-Deficient α,β-Unsaturated Amides via Epoxidation Using Oxone as a Dual Role Reagent

In organic synthesis, incorporating two functional groups into the carbon-carbon double bond of α,β-unsaturated amides is challenging due to the electron-deficient nature of the olefin moiety. Although a few examples of dihydroxylation of α,β-unsaturated amides have been demonstrated, producing cis-1,2-diols using either highly toxic OsO4 or other specialized metal reagents in organic solvents, they are limited to several specific amides. We describe herein a general and one-pot direct synthesis of trans-1,2-diols from electron-deficient α,β-unsaturated amides through dihydroxylation using oxone as a dual-role reagent in water. This reaction does not require any metal catalyst and produces non-hazardous and nontoxic K2 SO4 as the sole byproduct. Moreover, epoxidation products could also be selectively formed by adjusting the reaction conditions. By the strategy, the intermediates of Mcl-1 inhibitor and antiallergic bioactive molecule can be synthesized in one pot. The gram-scale synthesis of trans-1,2-diol which is isolated and purified by recrystallization further shows the potential applications of this new reaction in organic synthesis.

Decrease in Cell Viability of Breast Cancer Cells by a Di-Hydroxylated Derivative of N-(2-hydroxyphenyl)-2-Propylpentanamide

BACKGROUND

A preliminary study of the biotransformation by cytochrome P450 enzymes (CYP) of N-(2-hydroxyphenyl)-2-propylpentanamide (HO-AAVPA), an HDAC inhibitor, led to the synthesis of two hydroxylated derivatives: N-(2,4-dihydroxyphenyl)-2-propylpentanamide (5a) and N-(2,5-dihydroxyphenyl)-2-propylpentanamide (5b).

OBJECTIVE

The study aims to evaluate the anti-proliferative activity of these di-hydroxylated derivatives in breast cancer cell lines.

METHODS

MTT assays were conducted in MCF-7 and MDA-MB-231 cell lines. Additionally, in silico studies were carried out to evaluate the affinity of these derivatives with the HDAC1 enzyme.

RESULTS

Results showed that only 5b possess an enhanced anti-proliferative effect in breast cancer cell lines MCF-7 and MDA-MB-231. Docking studies revealed that the presence of hydroxyl groups, as well as the position of the additional hydroxyl groups, could have an impact on HDAC1 affinity and could explain the lack of activity of compound 5a.

CONCLUSION

A priori, these results hypothesize that anti-proliferative activity of 5b could be related to HDAC1 inhibition and thus anti-proliferative activity in breast cancer cells.

Chemical Synthesis of Modified Oligonucleotides Containing 5'-Amino-5'-Deoxy-5'-Hydroxymethylthymidine Residues

Introduction of cationic modifications into an oligonucleotide can increase its nuclease resistance and duplex- or triplex-forming abilities. In a recent study, we found that the nuclease resistance and RNA binding selectivity of an oligonucleotide containing a 5'-(R)-amino-5'-deoxy-5'-(R)-hydroxymethylthymidine residue were greater than those of the unmodified oligonucleotide. In this article, we describe the synthesis of 5'-amino-5'-deoxy-5'-hydroxymethylthymidine via dihydroxylation of the 5'-alkene derivative using either of two commercial AD (asymmetric dehydroxylation) mixes or via epoxidation and ring opening. We also provide detailed protocols for the syntheses of oligonucleotides containing 5'-amino-5'-deoxy-5'-hydroxymethylthymidine residues. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Synthesis of 5'-amino-5'-deoxy-5'-hydroxymethylthymidine phosphoramidites 9a and 9b Basic Protocol 2: Synthesis of oligonucleotides 1 and 2 containing 5'-amino-5'-deoxy-5'-hydoxymethylthymidine residues (_R T and _S T).

A Colorimetric Method for Quantifying Cis and Trans Alkenes Using an Indicator Displacement Assay

A colorimetric indicator displacement assay (IDA) amenable to high-throughput experimentation was developed to determine the percentage of cis and trans alkenes. Using 96-well plates two steps are performed: a reaction plate for dihydroxylation of the alkenes followed by an IDA screening plate consisting of an indicator and a boronic acid. The dihydroxylation generates either erythro or threo vicinal diols from cis or trans alkenes, depending upon their syn- or anti-addition mechanisms. Threo diols preferentially associate with the boronic acid due to the creation of more stable boronate esters, thus displacing the indicator to a greater extent. The generality of the protocol was demonstrated using seven sets of cis and trans alkenes. Blind mixtures of cis and trans alkenes were made, resulting in an average error of ±2 % in the percentage of cis or trans alkenes, and implementing E₂ and Wittig reactions gave errors of ±3 %. Furthermore, we developed variants of the IDA for which the color may be tuned to optimize the response for the human eye.

Total Syntheses of 11-Acetoxy-4-deoxyasbestinin D, 4-Deoxyasbestinin C, Asbestinin-10, -20, -21 and -23

Six members of the asbestinin family of marine diterpene natural products have been synthesized in an efficient and stereoselective manner from a single oxa‐bridged intermediate. Five of these natural products have not been synthesized previously and the structures of four of them have been confirmed as those proposed originally or following revisions to the original structures. The fifth natural product—asbestinin‐21—has been shown to be a diastereomer of the compound that had been proposed previously.

Synthesis, Structure, and Reactivity of Binaphthyl Supported Dihydro[1,6]diazecines

A short approach to chiral diaza-olefines from protected 2,2'-diamino-1,1'-binaphthyl is presented. Cis- and trans-olefines can be selectively obtained by twofold N-allylation followed by RCM or by bridging a 2,2'-diamino-1,1'-binaphthyl precursor with trans-1,4-dibromo-2-butene. Deprotection afforded cis- and trans-dihydro[1,6]diazecines 1 in 58 and 64% overall yield. The reactivity of the but-2-ene-1,4-diyl fragment was investigated yielding corresponding epoxides, diols, and mono- and dibromo products. In several cases rearrangements and participation of the proximate N-Boc group was observed. In no case could allylic substitution be accomplished. From 13 compounds X-ray structure analyses could be obtained.

Total Synthesis of Sphingofungin E and 4,5-Di-epi-sphingofungin E

Total synthesis of sphingofungin E and 4,5-di-epi-sphingofungin E was achieved from an intermediate same as that of myriocin and mycestericin D via antipodal stereoselective dihydroxylations.

Studies directed toward the exploitation of vicinal diols in the synthesis of (+)-nebivolol intermediates

While the exploitation of the Sharpless asymmetric dihydroxylation as the source of chirality in the synthesis of acyclic molecules and saturated heterocycles has been tremendous, its synthetic utility toward chiral benzo-annulated heterocycles is relatively limited. Thus, in the search for wider applications of Sharpless asymmetric dihydroxylation-derived diols for the synthesis of benzo-annulated heterocycles, we report herein our studies in the asymmetric synthesis of (R)-1-((R)-6-fluorochroman-2-yl)ethane-1,2-diol, (R)-1-((S)-6-fluorochroman-2-yl)ethane-1,2-diol and (S)-6-fluoro-2-((R)-oxiran-2-yl)chroman, which have been used as late-stage intermediates for the asymmetric synthesis of the antihypertensive drug (S,R,R,R)-nebivolol. Noteworthy is that a large number of racemic and asymmetric syntheses of nebivolol and their intermediates have been described in the literature, however, the Sharpless asymmetric dihydroxylation has never been employed as the sole source of chirality for this purpose.

Stereoselective synthesis of (+)-1-deoxyaltronojirimycin

A stereocontrolled, facile and high-yield approach for producing (+)-altroDNJ, has been developed starting from the inexpensive commercial cis 2-butene-1,4-diol. Sharpless epoxidation and a subsequent dihydroxylation were used for the introduction of all stereocentres; finally, the ring closure under basic conditions afforded the piperidine heterocycle.

Tandem Z-Selective Cross-Metathesis/Dihydroxylation: Synthesis of anti-1,2-Diols

A stereoselective synthesis of anti-1,2-diols has been developed using a multitasking Ru catalyst in an assisted tandem catalysis protocol. A cyclometalated Ru complex catalyzes first a Z-selective cross-metathesis of two terminal olefins, followed by a stereospecific dihydroxylation. Both steps are catalyzed by Ru, as the Ru complex is converted to a dihydroxylation catalyst upon addition of NaIO4. A variety of olefins were transformed into valuable, highly functionalized, and stereodefined molecules. Mechanistic experiments were performed to probe the nature of the oxidation step and catalyst inhibition pathways. These experiments point the way to more broadly applicable tandem catalytic transformations.

Enantioselective synthesis of polyhydroxyindolizidinone and quinolizidinone derivatives from a common precursor

A concise asymmetric synthetic route to two new tetrahydroxyindolizidinone and quinolizidinone derivatives has been developed from a common intermediate which featured a highly selective dihydroxylation reaction and a RCM reaction as key steps.

Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate

Esters of crotonic acid were brominated on a multigramme scale using a free radical procedure. A phase transfer catalysed fluorination transformed these species to the 4-fluorobut-2E-enoates reproducibly and at scale (48–53%, ca. 300 mmol). Asymmetric dihydroxylation reactions were then used to transform the butenoate, ultimately into all four diastereoisomers of a versatile fluorinated C₄ building block at high enantiomeric-enrichment. The (DHQ)₂AQN and (DHQD)₂AQN ligands described by Sharpless were the most effective. The development and optimisation of a new and facile method for the determination of ee is also described; ¹⁹F{¹H} spectra recorded in d-chloroform/diisopropyl tartrate showed distinct baseline separated signals for different enantiomers.

Simplified synthesis of individual stereoisomers of the 4-hydroxynonenal adducts of deoxyguanosine

We previously reported the synthesis of the 1,N²-deoxyguanosine adducts of 4-hydroxynonenal, an important product of lipid peroxidation, which involved the nucleophilic aromatic substitution reaction of an O⁶-protected-2-fluoroinosine with 4-amino-1,2,5-trihydroxydecanal followed by periodate oxidation of the vicinal diol.³ An improved synthesis of the amino triols has been developed. The syn and anti diasteromers of a key intermediate, 4-nitro-5-hydroxy-1-decene, were synthesized by a Henry reaction and separated; each diastereomer was further separated into individual enantiomers by chiral supercritical fluid chromatography. Of note, dihydroxylation of the terminal olefin under conventional conditions with catalytic OsO₄ and a tertiary amine oxide as the stoichiometric oxidant led to scrambling of stereochemistry at C4. The scrambling was not observed when t-butylhydroperoxide was used as the oxidant.

Osmium(III) and osmium(V) complexes bearing a macrocyclic ligand: a simple and efficient catalytic system for cis-dihydroxylation of alkenes with hydrogen peroxide

A simple protocol that uses [Os(III)(OH)(H2O)(L-N4Me2)](PF6)2 (1; L-N4Me2 = N,N'-dimethyl-2,11-diaza[3.3](2,6)pyridinophane) as a catalyst and H2O2 as a terminal oxidant for efficient cis-1,2-dihydroxylation of alkenes is presented. Unfunctionalized (or aliphatic) alkenes and alkenes/styrenes containing electron-withdrawing groups are selectively oxidized to the corresponding vicinal diols in good to excellent yields (46-99 %). In the catalytic reactions, the stoichiometry of alkene:H2O2 is 1:1, and thus the oxidant efficiency is very high. For the dihydroxylation of cyclohexene, the catalytic amount of 1 can be reduced to 0.01 mol % to achieve a very high turnover number of 5500. The active oxidant is identified as the Os(V)(O)(OH) species (2), which is formed via the hydroperoxide adduct, an Os(III)(OOH) species. The active oxidant 2 is successfully isolated and crystallographically characterized.