Alkyl Esters Research Articles

Increase of ibuprofen penetration through the skin by forming ion pairs with amino acid alkyl esters and exposure to the electromagnetic field

A method of increasing the permeability of ibuprofen through the skin using a rotating magnetic field (RMF) is presented. This study evaluated whether 50 Hz RMF modifies ibuprofen’s permeability through the skin. Ibuprofen and its structural modifications in the form of ibuprofenates of isopropyl esters of L-amino acids such as L-valine, L-phenylalanine, L-proline, and L-aspartic acid were used in the research. To this end, Franz cells with skin as membrane were exposed to 50 Hz RMF with 5% ibuprofen and its derivatives in an ethanol solution for 48 h. Following the exposures, the amount of penetrated compound was analysed. Regardless of the compound tested, a significant increase in drug transport through the skin was observed. The differences in the first 30 min of permeation are particularly noticeable. Furthermore, it was shown that using RMF increases the permeability of ibuprofen from 4 to 244 times compared to the test without the RMF. The greatest differences were observed for unmodified ibuprofen. However, it is noteworthy that the largest amounts of the active substance were obtained with selected modifications and exposure to RMF. The RMF may be an innovative and interesting technology that increases the penetration of anti-inflammatory and anti-ache drugs through the skin.

Palladium-Catalyzed 1,1-Alkynyloxygenation of 2-Vinylbenzoates with Alkynyl Bromides

The palladium-catalyzed reaction of alkyl 2-vinylbenzoates with silyl-protected alkynyl bromides leads to the selective production of 3-alkynylated isochroman-1-ones. The use of an alkyl ester group as an effective oxygen nucleophile is crucial for the efficient 1,1-alkynyloxygenation of alkenes.

Production of biodiesel from Phyllanthus emblica seeds using activated charcoal as heterogenous catalyst

Biodiesel can be a vital substitute for the traditional fossil fuels. Biodiesel is not only renewable but also contributes to environment by reducing greenhouse gas emission. But using edible crops as source for biofuel production can cause food security problems. In the present investigation, seeds of Phyllanthus emblicawhich is a nonedible source was used for biodiesel production. Seeds were collected and dried and then converted to thin powder which was used as feedstock. Oil extraction was optimized using different extraction methods. GC-FID was carried out for analysing the fatty acid profile of the extracted oil. Dimethyl carbonate was used instead of methanol and activated charcoal was used as catalyst for efficient biodiesel production. Activated charcoal was produced and analysed with FTIR and SEM to study about morphology of the activated charcoal. Transesterification reaction parameters were optimized. Temperature of 40, 60 and 80 °C, DMC to oil molar ratio of 2:1, 4:1, 6:1, 8:1 and catalyst concentration of 1.5, 2 and 2.5 wt% in relation to oil was carried out to find the efficient reaction conditions. GC–MS was carried out to confirm the presence of fatty acid alkyl esters.

Density Measurements and PC-SAFT Modeling for Beef Tallow Fatty Acid Methyl Esters (FAME Mixture) + Alkane up to 70 MPa

Biodiesel is mainly constituted by fatty acid alkyl esters, and the effect of adding alkane compounds is of great importance in order to analyze the changes in the thermophysical properties under high pressure that is of relevance in diesel engines. This work is aimed at the study of density behavior of two systems formed by beef tallow fatty acid methyl esters (FAME mixture) + alkane (decane or dodecane) in the temperature range of 303–393 K and in the pressure range of 0.2–68.29 MPa. Experiments were carried out by means of two vibrating tube densimeters with an expanded uncertainty in density of 0.7 kg·m–3. Transesterification of waste beef tallow by using methanol at supercritical conditions was used to obtain biodiesel. The FAME mixture was constituted by methyl tetradecanoate, methyl hexadecanoate, methyl octadecenoate, and methyl (Z)-octadec-9-enoate. Density behavior was correlated using the Tammann–Tait equation and modeled with the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state. Density correlation deviations using the Tammann–Tait equation were found to be less than 0.05% and 4.15 kg·m–3 for the average absolute deviation (AAD) and standard deviation (STD), respectively. The PC-SAFT modeling yielded an AAD = 0.11% and an STD = 1.15 kg·m–3. The behavior for density and the derived thermodynamic properties were explained in terms of the fatty acid methyl ester content.

The Inhibitory Effect of Gallic Acid Alkyl Esters on Lipid Oxidation of Intactly Soaked Oyster Meats and Oyster Meat Homogenates during Refrigerated Storage

AbstractIn this study, the antioxidant effects of gallic acid (GA) and its alkyl esters including methyl gallate (MG), butyl gallate (BG), octyl gallate (OG), and lauryl gallate (LG) in whole oyster meats and oyster meat homogenates during cold storage are investigated. The oxidation degree of lipid is measured by peroxide value (POV), thiobarbituric acid active substances (TBARS), and polyunsaturated fatty acid (PUFA) percentage. The results show that the lipid oxidation in the two types of samples is inhibited by GA alkyl esters, and the antioxidant effects first increase and then decrease along with the extension of the chain length, among the esters, BG and OG are relatively more effective. Therefore, it is speculated that the antioxidant capacity of GA alkyl esters may be influenced by hydrophobicity and follows a “cut‐off effect” in whole oyster meats and oyster meat homogenates.Practical application: Seafood is easily oxidized even under cold storage because it contains more PUFA. Antioxidants are widely used to inhibit lipid oxidation. In this study, the antioxidant capacity of GA alkyl esters in whole oyster meats and oyster meat homogenates is investigated, which improves the selection of suitable antioxidants to strengthen the oxidation stability of oyster samples for cold storage.

Toxicity of organophosphorus flame retardants

As the development and use of organophosphorus flame retardants have become more prevalent, concerns about potential toxicity are being raised. To date, most studies on potential toxicity have focused on simple phosphate esters and often include both alkyl and aryl esters or, in some cases, even halogenated phosphate esters (which should more properly be included among organohalogen flame retardants). The inclusion of several kinds of esters into a single study leads to muddled conclusions. Each class of phosphate esters should be subjected to toxicity assessment separately. Furthermore, the potential toxicity of the more effective (lower level of oxygenation at phosphorus: phosphonates, phosphinates, phosphine oxides) organophosphorus flame retardants has been little explored. The few results available suggest that these compounds exhibit no or minimal toxicity (lower than that of phosphates?). This represents an area that should be the focus of careful detailed studies to establish any potential toxicity.

Production of Methanol Tolerant Cell-bound Lipase of Magnusiomyces spicifer SPB2 and Application as Whole-cell Biocatalyst in Transesterification Reaction

Cell-bound lipase (CBL) is a potential biocatalyst for production of fatty acid alkyl ester (FAAE), which is feasible replacement for diesel fuel. This study aimed to improve both hydrolysis and transesterification activities of CBL from the yeast Magnusiomyces spicifer SPB2, which could be employed as whole-cell biocatalyst for transesterification reactions through optimizing the growth medium using Taguchi orthogonal array experimental method (L9). The optimized medium, resulting the highest CBL transesterification activity, consisted of soybean oil, peptone, Gum Arabic and an initial pH of 5. Interestingly, the fatty acid methyl ester (FAME) yield increased up to 33.28 times when compared with non-optimized medium. Moreover, cell morphology of M. spicifer SPB2 varied depending on the culture medium component. The single cell was more active to be used as the whole-cell biocatalyst than the pseudomycelial form for transesterification reaction. The highest FAME yield was 93.86 % when refined palm oil to methanol molar ratio of 1:8 was used as substrates. Whole-cell lipase from M. spicifer showed favorable activity to iso-butanol as an acyl accepter, resulting in fatty acid butyl ester (FABE) yield of 86.80 % at 1:3 molar ratio of palm oil to iso-butanol. The FAME and FABE yields dramatically decreased from 93.86 and 86.80 % to 57.02 and 4.48 %, respectively after the reuse of the enzyme to the second batch of reaction. These results indicated that the whole-cell biocatalyst developed from M. spicifer was an efficient and economical approach to improve enzyme activity and stability in the transesterification reaction. HIGHLIGHTS Methanol tolerant cell-bound lipase and extracellular lipase of spicifer SPB2 were produced The whole-cell biocatalyst of spicifer SPB2 was developed for FAME production The optimized medium was developed to prepare whole-cell lipases from spicifer SPB2 Gum Arabic was the most influencing factor for synthetic activity of whole-cell CBL from yeast Single cell morphology exhibited higher transesterification activity than pseudomycelial form GRAPHICAL ABSTRACT

Cover Feature: Balancing Attraction and Repulsion: The Influence of London Dispersion in [10]Cycloparaphenylene‐Fullerene Complexes (Chem. Eur. J. 20/2023)

Molecular interactions are a combination of different attractive and repulsive forces. We have studied the delicate balance within a supramolecular [10]cycloparaphenylene–fullerene complex—both functionalized with alkyl esters—to evaluate the attractive and repulsive interplay between the substituents on the components. More information can be found in the Research Article by H. A. Wegner and co-workers (DOI: 10.1002/chem.202300268).

THE CHEMICAL COMPOSITION OF PARABEN AND ITS EFFECTS ON HEALTH

Parabens are a group of alkyl esters of p-hydroxybenzoic acid and usually include methyl paraben, ethyl paraben, propyl paraben, butyl paraben, isobutyl paraben, isopropyl paraben and benzyl paraben. Parabens (or their salts) are widely used as preservatives in cosmetics and medicine due to their relatively low toxicity and long history of safe use. Testing of parabens has shown, to varying degrees, that individual paraben compounds have weak estrogenic activity in some in vitro screening tests, such as estrogen receptor ligand binding, regulation of CAT gene expression, and proliferation of MCF-7 cells. Reported in vivo effects include uterine weight gain (eg, butyl, isobutyl, and benzyl parabens) and male reproductive tract effects (eg, butyl and propyl parabens). However, in relation to estrogen as a control during in vivo studies, parabens are much less active than estrogen. While exposure to sufficient doses of exogenous estrogens can increase the risk of certain adverse effects, it is hypothesized that similar risks may arise from exposure to much weaker endocrine-active chemicals (EACs) is still speculation. In evaluating the possibility that exposure to weakly active EACs may be associated with adverse effects due to their endocrine mode of action, it is important to consider both the dose and potency of these compounds compared to estrogen. In this review, a comparative approach involving dose and potency is used to assess whether in utero or adult exposure to parabens may be associated with adverse effects due to their estrogen-modulating mode of action. Keywords: parabens, p-Hydroxybenzoates, PHBA, paraben applications, Methyl paraben.

Diversified chemical profiles of cuticular wax on alpine meadow plants of the Qinghai-Tibet Plateau.

The alpine meadow plants showed great intra- and inter-genera variations of chemical profiles of cuticular waxes. Developing an understanding of wax structure-function relationships that will help us tackle global climate change requires a detailed understanding of plant wax chemistry. The goal in this study was to provide a catalog of wax structures, abundances, and compositions on alpine meadow plants. Here, leaf waxes from 33 plant species belonging to 11 families were sampled from alpine meadows of the east side of the Qinghai-Tibet Plateau. Across these species, total wax coverage varied from 2.30μgcm-2 to 40.70μgcm-2, showing variation both within as well as between genera and suggesting that wax variation is subject to both environmental and genetic effects. Across all wax samples, more than 140 wax compounds belonging to 13 wax compound classes were identified, including both ubiquitous wax compounds and lineage-specific compounds. Among the ubiquitous compounds (primary alcohols, alkyl esters, aldehydes, alkanes, and fatty acids), chain length profiles across a wide range of species point to key differences in the chain length specificity of alcohol and alkane formation machinery. The lineage-specific wax compound classes (diols, secondary alcohols, lactones, iso-alkanes, alkyl resorcinols, phenylethyl esters, cinnamate esters, alkyl benzoates, and triterpenoids) nearly all consisted of isomers with varying chain lengths or functional group positions, making the diversity of specialized wax compounds immense. The comparison of species relationships between chemical data and genetic data highlighted the importance of inferring phylogenetic relationships from data sets that contain a large number of variables that do not respond to environmental stimuli.

The Skin-Whitening and Antioxidant Effects of Protocatechuic Acid (PCA) Derivatives in Melanoma and Fibroblast Cell Lines.

The skin is the most voluminous organ of the human body and is exposed to the outer environment. Such exposed skin suffers from the effects of various intrinsic and extrinsic aging factors. Skin aging is characterized by features such as wrinkling, loss of elasticity, and skin pigmentation. Skin pigmentation occurs in skin aging and is caused by hyper-melanogenesis and oxidative stress. Protocatechuic acid (PCA) is a natural secondary metabolite from a plant-based source widely used as a cosmetic ingredient. We chemically designed and synthesized PCA derivatives conjugated with alkyl esters to develop effective chemicals that have skin-whitening and antioxidant effects and enhance the pharmacological activities of PCA. We identified that melanin biosynthesis in B16 melanoma cells treated with alpha-melanocyte-stimulating hormone (α-MSH) is decreased by PCA derivatives. We also found that PCA derivatives effectively have antioxidant effects in HS68 fibroblast cells. In this study, we suggest that our PCA derivatives are potent ingredients for developing cosmetics with skin-whitening and antioxidant effects.

Fatty Acid Alkyl Ester Production by One-Step Supercritical Transesterification of Beef Tallow by Using Ethanol, Iso-Butanol, and 1-Butanol

The effect of temperature was studied on the synthesis of fatty acid alkyl esters by means of transesterification of waste beef tallow using ethanol and, iso-butanol and 1-butanol at supercritical conditions. These alcohols are proposed for the synthesis of biodiesel in order to improve the cold flow properties of alkyl esters. Alcohol–beef tallow mixtures were fed to a high-pressure high-temperature autoclave at a constant molar ratio of 45:1. Reactions were carried out in the ranges of 310–390 °C and 310–420 °C for ethanol and iso-butanol, respectively; meanwhile, synthesis using 1-butanol was assessed only at 360 °C. After separation of fatty acid alkyl esters, these samples were characterized by nuclear magnetic resonance (NMR) and gas chromatography coupled to mass spectrometry (GC-MS) to quantify yields, chemical composition, and molecular weight. Results indicated that yields enhanced as temperature increased; the maximum yields for fatty acid ethyl esters (FAEEs) were attained at 360 °C, and for fatty acid butyl esters (FABEs) were achieved at 375 °C; beyond these conditions, the alkyl ester yields reached equilibrium. Concerning the physicochemical properties of biodiesel, the predicted cetane number and cloud point were enhanced compared to those of fatty acid methyl esters.

Presence of methyl paraben in anti-diabetic herbal preparations

Plant-based hypoglycemic therapeutics have been increasing in consumption due to the escalation of type 2 diabetes and its related complications. However, the safety of the preparations is little understood. Parabens (alkyl esters of p-hydroxybenzoic acid) are widely used as preservatives in these pharmaceuticals. However, the presence of methylparaben in formulations raises anxiety due to its potential endocrine disruption functions. Endocrine disruption could lead to undesirable health abnormalities and carcinogenic, estrogenic, and adverse reproductive effects. The present investigation directs toward estimating of methylparaben in some anti-diabetic herbal preparations using UV- Vis spectrophotometric method abiding by International Conference on Harmonization (ICH) guidelines for validation. The analytical wavelength of methylparaben in methanol was determined and found at 256.5 nm. The method obeys Beer’s law in the analytical range and has a good coefficient of determination (r2= 0.9881). The limit of detection (LOD) and limit of quantification (LOQ) were 0.19 ppm and 0.57 ppm, respectively. Recoveries were 91.3-98.8% in analyte-free plant matrix and 91-105.8 % in a diluent. The coefficient of variation (CV%) varied between 0.005- 0.268% for different standards. Results of forty-eight anti-diabetic herbal preparations showed methylparaben was detected in thirty-four samples in the range of 13.12 – 325.13 mg/day with a mean exposure value of 78.25 mg/day. However, none of the samples raise concerns about safety (the safety ceiling for paraben is 420 mg/day). More investigation is required to determine, whether the herbal drugs are safe to consume in terms of methylparaben. J. Asiat. Soc. Bangladesh, Sci. 48(1-2): 41-52, June-December 2022

CeO2‐Nanorods‐Catalyzed Protoboration of Alkenes and Alkynes with Bis(pinacolato)diboron

AbstractThe protoboration of alkenes and alkynes with B2pin2 (pin=OCMe2CMe2O) using a heterogeneous CeO2 nanorods catalyst has been developed to afford the corresponding alkyl and vinyl boronate esters in 41–99% yield under mild reaction conditions. A series of aromatic and aliphatic alkenes and alkynes with synthetically important functional groups were well tolerated. In both the systems, the catalyst could be reused for up to six runs without significant loss in activity. Stoichiometric reactions revealed that the protoboration may proceed through the in situ formed catalytically active boryl species.magnified image

Separation and direct-indirect analysis of six group components from liquids of kerosene co-refining

The composition and structure of kerosene co-refining products (KCR) need to be studied to promote their further processing and utilization besides for making fuels. In this paper, their composition and structure were analyzed layer by layer from top to bottom in the form of “Surface (KCR)-Line (six group components, SGCs)-Point (compounds)”. SGCs combine extraction and column chromatography to provide a method for highly efficient separation of heavy hydrocarbons. Insoluble components (asphaltene, ASP) and n-heptane soluble (HS) were obtained from light and heavy liquids (LP and HP) of KCR by Soxhlet extraction. HS was gradient eluted by chromatographic column with different solvents and α-Al2O3, and separated into other five group components: saturates (SA), aromatics (AR), heteroatoms (HE), phenolics (PH) and resins (RE), wherein the results show that the extraction yields of LP-SA, LP-AR, LP-PH, LP-RE are 68.53 wt%, 7.28 wt%, 3.55 wt% and 1.20 wt%, and the extraction yields of HP-SA, HP-AR, HP-HE, HP-PH, HP-RE are 36.06 wt%, 25.13 wt%, 6.27 wt%, 4.53 wt% and 2.37 wt%, respectively. Physical and chemical characterization of the raw materials and SGCs were analyzed by TG, FTIR, 13C NMR, GC/MS, and Py-GC/MS, in which the combination of GC/MS and Py-GC/MS can fully detect the light and heavy components in LP and HP, including those difficult to detect above 300 °C. The final thermal mass loss rates of these components follow the order of LP-SA > LP-AR > LP-PH > LP-RE and HP-SA > HP-AR > HP-PH > HP-HE > ASP > HP-RE. The aromatic carbon mass ratio (fa) of LP and HP is 15.27% and 19.45%, respectively. n-Alkanes (C11–32) are the main compounds in LP and HP, followed by polycyclic aromatics with 3–4 R. Aromatics are rich in -CH2- bridge bond to generate light aliphatics and aromatics at 500 °C, especially the ASP generates many monocyclic aromatics with the increase of temperature by Py-GC/MS. In addition to aliphatics and aromatics, alkyl phenols, esters, pyridines and thiophenes are the main compounds in LP and HP.

Techno-Economic Analysis of Interesterification for Biodiesel Production

Interesterification is an alternative reaction for the production of fatty acid alkyl esters from triglycerides, a pathway that avoids unwanted byproduct formation. In this work, the technical and economic feasibility of soybean oil interesterification for biodiesel production on a commercial scale is assessed. The interesterification kinetics of triolein (model soybean oil) and methyl acetate using ferric sulfate as a heterogeneous acid catalyst are experimentally determined, and the results are used to parameterize a kinetic model. Process simulations are developed using Aspen Plus V11 for acid and alkaline heterogeneously catalyzed interesterification plants at varying production rates and methyl acetate-to-oil molar ratios (MAOMRs). At all production capacities and MAOMRs tested, the acid-catalyzed processes are found to have more favorable process energy consumption and profitability metrics compared to the alkaline-catalyzed processes. The most economically promising design operates at a production capacity of 30,000 metric tons/yr and an MAOMR of 10:1 with a net present value of $34 million after 20 years and a biodiesel breakeven price of $0.78/kg. This case has a process energy demand of 35,000 MJ/h, resulting in a process energy ratio of 0.25. This work indicates that interesterification shows commercial viability and is a promising alternative to transesterification for biodiesel production.

Interfacial behavior of gallic acid and its alkyl esters in stripped soybean oil in combination with monoacylglycerol and phospholipid

The effect of gallic acid alkyl esters and their combination with monoacylglycerol (MAG) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) on the formation of hydroperoxides and hexanal were determined during the oxidation of stripped soybean oil. Interfacial tension, water content, and droplet size were evaluated to monitor the physical properties of the oil system. Adding MAG and DOPC, especially MAG/DOPC, to the oil promoted the partitioning of antioxidants into the water–oil interfaces by further reducing the interfacial tension. The stripped oil containing methyl gallate (MG) accompanied by MAG/DOPC had lower values of the critical micelle concentration of hydroperoxides and larger micellar size at the induction period. This confirms that MG was able to more effectively reduce the free hydroperoxides concentration and inhibit them in an interfacial way. The conjunction of surfactants has been shown as a promising strategy to improve the interfacial and antioxidant activity of gallates in the oxidative stability of soybean oil.

Synthesis and biological evaluation of salophen nickel(II) and cobalt(III) complexes as potential anticancer compounds.

Recent in vitro investigations of N,N'-bis(salicylidene)-1,2-phenylenediamine (SAP) iron(III) complexes substituted with alkyl (ethyl, propyl, butyl) carboxylates at position 4 in tumor and leukemia cells revealed strong cytotoxic activity. In continuation of this study, analogous nickel(II) and cobalt(III) complexes were synthesized and tested in HL-60 leukemia, and cisplatin-sensitive and -resistant A2780 ovarian cancer cell lines. The biological activity depended on the extent of cellular uptake and the formation of reactive oxygen species (ROS). Inactive [(Ni(II)SAP] complexes (1-3) only marginally accumulated in tumor cells and did not induce ROS. The cellular uptake of [Co(III)SAP]Cl complexes (4-6) into the cells depended on the length of the ester alkyl chain (ethyl, 4 < propyl, 5 < butyl, 6). The cytotoxicity correlated with the presence of ROS. The low cytotoxic complex 4 induced only few ROS, while 5 and 6 caused a good to outstanding antiproliferative activity, exerted high ROS generation, and induced cell death after 48 h. Necrostatin-1 prevented the biological effects, proving necroptosis as part of the mode of action. Interestingly, the effects of 5 and 6 were not reversed by Ferrostatin-1, but even enhanced upon simultaneous application to the tumor cells.

Betaine- and L-Carnitine-Based Ionic Liquids as Solubilising and Stabilising Agents for the Formulation of Antimicrobial Eye Drops Containing Diacerein.

The therapeutic efficacy of topically administered drugs, however powerful, is largely affected by their bioavailability and, thus, ultimately, on their aqueous solubility and stability. The aim of this study was to evaluate the use of ionic liquids (ILs) as functional excipients to solubilise, stabilise, and prolong the ocular residence time of diacerein (DIA) in eye drop formulations. DIA is a poorly soluble and unstable anthraquinone prodrug, rapidly hydrolysed to rhein (Rhe), for the treatment of osteoarthritis. DIA has recently been evaluated as an antimicrobial agent for bacterial keratitis. Two ILs based on natural zwitterionic compounds were investigated: L-carnitine C6 alkyl ester bromide (Carn6), and betaine C6 alkyl ester bromide (Bet6). The stabilising, solubilising, and mucoadhesive properties of ILs were investigated, as well as their cytotoxicity to the murine fibroblast BALB/3T3 clone A31 cell line. Two IL-DIA-based eye drop formulations were prepared, and their efficacy against both Staphylococcus aureus and Pseudomonas aeruginosa was determined. Finally, the eye drops were administered in vivo on New Zealand albino rabbits, testing their tolerability as well as their elimination and degradation kinetics. Both Bet6 and Carn6 have good potential as functional excipients, showing solubilising, stabilising, mucoadhesive, and antimicrobial properties; their in vitro cytotoxicity and in vivo ocular tolerability pave the way for their future use in ophthalmic applications.

Z-Trisubstituted α,β-Unsaturated Esters and Acid Fluorides through Stereocontrolled Catalytic Cross-Metathesis.

Catalytic cross-metathesis (CM) reactions that can generate trisubstituted alkenes in high stereoisomeric purity are important but remain limited in scope. Here, CM reactions are introduced that generate Z-trisubstituted α-methyl, α,β-unsaturated, alkyl and aryl esters, thiol esters, and acid fluorides. Transformations are promoted by a Mo bis-aryloxide, a monoaryloxide pyrrolide, or a monoaryloxide chloride complex; air-stable and commercially available paraffin tablets containing a Mo complex may also be used. Alkyl, aryl, and silyl carboxylic esters as well as thiol esters and acid fluoride reagents are either purchasable or can be prepared in one step. Products were obtained in 55-95% yield and in 88:12->98:2 Z/E ratio (typically >95:5). The applicability of the approach is highlighted by a two-step conversion of citronellol to an isomintlactone precursor (1.7 g, 73% yield, and 97:3 Z/E) and a single-step transformation of lanosterol acetate to 3-epi-anwuweizic acid (72% yield and 94:6 Z/E). Included are the outcomes of DFT studies, regarding several initially puzzling catalyst activity trends, providing the following information: (1) it is key that a disubstituted Mo alkylidene, generated by a competing homo-metathesis (HM) pathway, can re-enter the productive CM cycle. (2) Whereas in a CM cycle the formation of a molybdacyclobutane is likely turnover-limiting, the collapse of related metallacycles in a HM cycle is probably rate-determining. It is therefore the relative energy barrier required for these steps that determines whether CM or HM is dominant with a particular complex.