Quadrant Rule Research Articles

Population Dynamics and Stock Status of the Round Sardinella (Sardinella aurita, Valenciennes, 1847) in the Coastal Waters of Côte d’Ivoire (West Africa)

This work was carried out to fill for a short time the lack of available data on the dynamic of Sardinella aurita within Côte d’Ivoire’s coastal waters. A total of 2000 samples of S. aurita were collected from May 2022 to April 2023, measured for total lengths and examined using FiSAT II. The asymptotic length (L∞) and growth rate (K) were 31.50 cm and 0.78 year-1 respectively implying that this species is a fast-growing and a shot live species. The lengths at first maturity and first capture were estimated at 18.49 cm and 23.42 cm respectively. The natural mortality rate (M=1.49 year-1) was higher than the fishing mortality rate (F=0.61year-1). The recruitment trend was continuous throughout the year with two major peaks showing the presence of strong recruitment into the stock. However, the exploitation rate (E=0.29) was lower than the 0.5. Furthermore, using the Quadrant rule, the investigated stock was categorized as underexploited. However, the current exploitation rate is higher than E0.5 inviting us to be more careful and to take appropriate measures.

Neolignans from Myristica fragrans seeds, revision of their absolute configurations, reduction products and biological activities

Chromatographic purification of the CH2Cl2 extract of Myristica fragrans seeds provided 19 known compounds, four dihydrofuran neolignans, licarines A, B and maceneolignans A, B were among the isolates. Prior to hydrogenation, in order to obtain their di- and tetrahydrogenated products, the absolute configuration of these compounds was thoroughly investigated based on their optical rotations and ECD spectra. This report provides evidences concerning the disagreement between the use of an aromatic quadrant rule and time-dependent density function theory calculation for the prediction of the absolute configurations at C-7 and C-8 in these dihydrobenzofuran neolignans. The absolute configurations of licarines A, B and maceneolignans A, B were subsequently redefined. The antimicrobial and cytotoxic activities of the isolates and reduction products of licarines A, B and maceneolignans A, B were also investigated.

Population dynamics of deep-water pink shrimp (Parapenaeus long-irostris Lucas, 1846) (Decapoda, Penaeidae) in the coastal waters of Tuzla (Eastern part of the Sea of Marmara)

In this study, the population parameters, recruitment period, exploitation rate, and stock status of deepwater pink shrimp (Parapenaeus longirostris Lucas, 1846) in the eastern Sea of Marmara were investigated. Growth showed negative allometry, and, b-values were signifi-cantly lower than 3 for females′ and males′ (p < 0.05). Females and males' growth performance indexes (φ) of P. longirostris were determined as 2.91 and 2.89, respectively. Asymptotic carapace lengths (CL∞), growth coefficients (K), and theoretical birth ages (t0) of females and males were calculated as 32.55, 28.67 mm, and 0.760, 0.950, and –0.233, –0769, respectively. The maximum exploitation rates (Emax) were calculated as 0.82 for females and as 0.90 for males. The first capture lengths (CL50) for females and males were estimated to be 18.78 and 18.07 mm, respectively. Two recruitment periods were determined for P. longirostris for females and males. The recruitment period was estimated to be between February and April, July and November. The yield perrecruit (YPR) analysis for females and males revealed that E0.1 = 0.72 and 0.80 approached the maximum exploitation rate (Emax = 0.82 and 0.90), respectively, indicating that exploitation for P. longirostris was in quadrant category "C" in the Eastern Marmara Sea. This status demonstrated active fishing, according to the quadrant rule.

Population dynamics of Sardinella aurita (Val., 1847) within Ghana’s coastal waters

Following the declining stocks of Sardinella aurita within the coastal waters of Ghana, this study aimed at examining some population parameters of Sardinella aurita as a guide for managing this important stock sustainably. Length-frequency data of 717 samples were obtained from June, 2014 to January 2015 and measured for total length with the resultant data analyzed using FiSAT II. The asymptotic length (L∞) and growth rate (K) were 21.53 cm SL and 0.25yr-1 respectively. The theoretical age at birth (t0), longevity (tmax) and growth performance index (ϕ) were -0.74yr-1, 12 years and 1.849 respectively. Total mortality rate (Z), natural mortality rate (M) and fishing mortality rate (F) were 3.17, 0.76 and 2.41yr-1 respectively. The ages at first recruitment and first capture signaled future collapse of the stock, in the absence of proper management interventions. VPA outcome showed that mid- lengths of 11 cm and 12 cm SL experienced the highest harvesting rate with MSY estimated at 7733 tons. The recruitment pattern was continuous with two major recruitment pulses. Exploitation rate (Ecurr=0.76) was higher than the maximum exploitation rate (Emax=0.56), indicating unsustainable exploitation. Further, the fishing regime fell within the overfished stage based on the Quadrant Rule. For sustainable exploitation of this commercial fish species, implementation of relevant biological reference points through reduction in fishing efforts, creation of marine protected areas and mesh size regulation are urgently advocated.Res. Agric. Livest. Fish.4(3): 237-248, December 2017

Population Dynamics of Bigeye Grunt, Brachydeuterus auritus (Valenciennes, 1831) in Ghana and Management Implications

Population dynamics of Brachydeuterus auritus harvested from Ghana’s coastal waters was assessed following pervious indications that this important species is collapsing. In view of this, a total of 849 samples of B. auritus were collected from February 2016 to January 2017, measured for total lengths and examined using FiSAT II. The mean length was 13.7 cm with a growth pattern of 2.8. The asymptotic length (L∞) and growth rate (K) were 21.53 cm and 0.67 yr-1 respectively portraying that this species is a faster growing species. The lengths at first maturity and capture were calculated as 14.4 cm and 6.02 cm respectively which indicated the presence of growth overfishing. The critical length at capture (Lc=0.28) was lower than 0.5, supporting the earlier assertion that the investigated fish species is plagued with growth overfishing. Natural mortality rate (M=1.44/yr) was higher than fishing mortality rate (F=1.22/yr) an indication that small sized fished fishes were largely harvested. The recruitment layout was unremitting throughout the year with two major peaks showing the presence of strong recruitment into the stock - a strategy to avert extinction of its species. However, the exploitation rate (E=0.46) was slightly lower than the Emax (0.52) showing that the biomass of the investigated stock could surpass the maximum sustainable yield (Emax) if necessary fishery management options are not put in place. Furthermore, using the Quadrant rule, the investigated stock was categorized as developing, hence any unsustainable increase in fishing efforts could facilitate growth overfishing leading to its collapse. Therefore, to ensure sustainable exploitation and contribution to protein requirement for coastal community households, relevant fishing measures are advocated.

Aspects of population dynamics of Red Pandora, Pagellus bellottii (Steindachner, 1882) from the coastal waters of Ghana

Population parameters for Red Pandora, Pagellus bellottii (Steindachner, 1882) from the eastern coastline of Ghana, using length-frequency data from June 2014 to January 2015 were assessed. A total of 440 samples of Pagellus bellottii were measured for standard length and analyzed with FiSAT II. The asymptotic length (L∞) and growth rate (K) were 19.43 cm and 0.42 per year. Theoretical age at birth (t0 ) and growth performance index (ϕ) were -0.44 per year and 2.20. The age at first maturity (tm50) and longevity (tmax) were 2.2 years and 7 years. The Bhattacharya’s method revealed three modal lengths groups: 9.3 cm, 12.1 cm, and 14.6 cm. Total mortality rate (Z), natural mortality rate (M) and fishing mortality rate (F) were 2.58 per year, 1.10 per year, and 1.48 per year. Exploitation rate (Ecurrent) and maximum exploitation rate (Emax) were estimated as 0.57 and 0.93 respectively. The recruitment pattern was continuous with two major recruitment pulses. VPA outcome showed that midlengths of 11.5 cm and 12.5 cm experienced the highest harvesting rate. The fishing regime of Pagellus bellottii fell in the developed stage based on the quadrant rule. Maximum Sustainable Yield (MSY) was 7864.18 tons. Results from the study indicated the existence of growth overfishing with the present state of exploitation as a forewarning to the collapse of the fishery in future. With resilience of Red pandora within the medium category, incidence of overfishing will produce economic consequences. The developed stage of fishing suggested that maximization of yield per recruits will lead to low stock biomass of Red pandora.

ChemInform Abstract: The Role of Deuterium in Optical Activity: The CD Spectrum of (S,S)- Dideuteriooxirane.

The circular dichroism of (S,S)-[2,3-{sup 2}H{sub 2}]oxirane has been investigated in the gas phase over the 1800-1500-{angstrom} region. While the absorption spectrum reveals only two allowed transitions, the circular dichroism (CD) spectrum shows a third transition which is magnetic dipole allowed and electric dipole forbidden. The CD sign of the first excited state complies with a quadrant rule which was formulated for the oxirane chromophore. This consignate behavior is contrary to the role of deuterium in carbonyl compounds, where an antioctant behavior is observed. The signs of the CD signals of the first excited state for oxiranes with methyl or deuterium substituents located in the same quadrant are the same, in contrast to the antioctant behavior of deuterium in carbonyls. This leaves the chirality rule formulated for substituted oxiranes without any exceptions. 33 refs., 1 fig.

4-Arylflavan-3-ols as Proanthocyanidin Models: Absolute Configuration via Density Functional Calculation of Electronic Circular Dichroism

Density functional theory/B3LYP has been employed to optimize the conformations of selected 4-arylflavan-3-ols and their phenolic methyl ether 3-O-acetates. The electronic circular dichroism spectra of the major conformers have been calculated using time-dependent density functional theory to validate the empirical aromatic quadrant rule applied to the assignment of the absolute configuration of this class of compounds. The modest 6-31G* basis set was sufficient to produce reasonable spectra. The calculated Cotton effects at 220-240 nm, crucial for the assignment of the C-4 absolute configuration, result from electronic transitions of the molecular orbitals involving the pi-electrons of the spatially close aromatic A-ring and 4-aryl moieties. The sign of this Cotton effect is determined by the orientation of the 4-aryl substituent: the negative and positive Cotton effects are associated with 4alpha- and 4beta-aryl substituents, respectively.

Circular dichroism of diglycosyl dichalcogenides in solution and solid state

Solution and solid-state CD spectra of nine peracetylated and deacetalyted diglycosyl disulfides were measured to study the relationship between the low-energy CD transitions (n1-->sigma*(S--S) and n2-->sigma*(S--S)) and helicity of the inherently chiral disulfide chromophore as perturbed by chiral carbohydrate moieties. The solid-state CD spectra were directly correlated with the reported X-ray structures of Ac4GlcSSGlcAc4 and Ac4GlcSSGalAc4, and the CD data revealed that all the disulfides have M helicity with C1--S--S--C1' dihedral angles -90 degrees < phi < 0 degrees both in solution and in the solid state. A TDDFT CD study was carried out on dimethyl diselenide which confirmed that the same quadrant rule is relevant between the signs of the low-energy CD transitions and the diselenide torsional angle as formulated previously for the disulfide chromophore. The CD spectra of Ac4GlcSeSeGlcAc4 measured in solution and in the solid state were correlated with its X-ray structure and reproduced well by TDDFT CD calculations performed on its tetra-O-acetyl derivative.

Modular P‐Chirogenic Aminophosphane‐Phosphinite Ligands for Rh‐Catalyzed Asymmetric Hydrogenation: A New Model for Prediction of Enantioselectivity

AbstractAn original series of P‐chirogenic aminophosphane‐phosphinite (AMPP) ligands has been synthesized from (+)‐ or(–)‐ephedrine in 23 to 61 % overall yields by a versatile three‐step methodology. The AMPP ligands, bearing either one or two P‐chirogenic centers, were used in the form of rhodium complexes for the catalyzed hydrogenation of α‐acetamidocinnamate as a test reaction. Notably, even with AMPP ligands all derived from (+)‐ephedrine, variation of the substituent on a P‐center allowed the phenylalanine derivatives to be obtained in either (S) or (R) absolute configurations, with ee values ranging from 99 % (S) to 88 % (R). The asymmetric induction was analyzed with the aid of X‐ray structures of AMPP complexes, and a new model for the enantioselectivity, taking into consideration the boat conformation and the steric and electronic dissymmetries at the dihydride rhodium‐substrate complex, has been proposed. This model offers an alternative to the quadrant rule, well adapted to the C2‐symmetry ligands and the chair conformation of their complex derivatives. In this work, the model, which schematizes the front side of the complex as a sextant in the direction of the cardinal points, fits with coordination of the substrate by the acetamido and the cinnamyl groups in the north and east (or west) parts, respectively. The enantioselectivity originates from the ligand residues located at the south‐east or south‐west parts of the dihydride rhodium intermediate. Computer modeling on several AMPP‐rhodium complexes with PCModel confirms the proposed predicting model.(© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2007)

SAC and SAC−CI Calculations of Excitation and Circular Dichroism Spectra of Straight-Chain and Cyclic Dichalcogens

Accurate quantum-chemical calculations of the excitation energies and the rotatory strengths of dichalcogens R-Ch-Ch-R (Ch = S, Se, Te) were carried out with the symmetry adapted cluster (SAC) and SAC-configuration interaction (CI) methods. A series of straight-chain molecules (dihydrogen dichalcogenide, dimethyl dichalcogenide, and (+)-bis(2-methylbutyl) dichalcogenide) and one cyclic molecule (2,3-(R,R)-dichalcogenadecalin) were adopted for comparative analysis. The calculated excitation and circular dichroism (CD) spectra were in good agreement with experimental ones (Laur, P. H. A. In Proceedings of the Third International Symposium on Organic Selenium and Tellurium Compounds; Cagniant, D., Kirsch, G., Eds.; Universite de Metz: Metz, 1979; pp 219-299) within 0.3 eV. The fitting CD spectra also reasonably reproduced the experimental ones. In all the molecules adopted, the first and second lowest bands were assigned to the n-sigma(Ch-Ch) transition and the third and fourth lowest bands to the n-sigma(Ch-R) transition. The first and second lowest bands apparently depended on the R-Ch-Ch-R dihedral angle, suggesting that the orbital energies of two sigma(Ch-Ch) change with the R-Ch-Ch-R dihedral angle. This calculated trend agrees with two empirical rules: the C(2) rule and the quadrant rule.

Conformational Analysis and CD Calculations of Methyl-Substituted 13-Tridecano-13-lactones

Conformational models covering an energy range of 3 kcal/mol were calculated for (13S)-tetradecano-13-lactone (3), (12S)-12-methyltridecano-13-lactone (4), and (12S,13R)-12-methyltetradecano-13-lactone (8), starting from a semiempirical Monte-Carlo search with AM1 parametrization, and subsequent optimization of the 100 best conformers at the 6-31G*/B3LYP and then the TZVP/B3LYP level of density-functional theory. CD Spectra for these models were calculated by the time-dependent DFT method with the same functional and basis sets as for the ground-state calculations and Boltzmann weighting of the individual conformers. The good correlation of the calculated and experimental spectra substantiates the interpretation of these conformational models for the structure–odor correlation of musks. Furthermore, the application of the quadrant rule in the estimation of the Cotton effect for macrolide conformers is critically discussed.

Chiroptical Properties of the Protoverbine Class of Macrocyclic Spermine Alkaloids

The chiroptical properties (circular dichroism, CD) of the 17-membered macrocyclic spermine lactam alkaloids (−)-protoverbine (16), its N,N′-methylene-bridged natural analogue (+)-protomethine (17), their natural derivatives (−)-verbacine (1), (−)-verballocine (2), (−)-verbascenine (3), (−)-verballoscenine (4), (+)-verbamethine (5), (+)-incasine C (6), (+)-verdoline (incasine B′, 30), (+)-incasine B (31), and some of their isosteric analogues were studied. By chemical and chiroptical correlation, it was confirmed that an amidically bonded (S)-β-phenyl-β-alanine fragment forms the chiral moiety in all of these natural compounds. The signs of the registered Cotton effects (CEs) are interpreted in terms of the Smith's quadrant rule for the 1Lb CEs of chiral α-substituted benzylamines and the Ogura's sign rule for n → π* CEs of lactams. Some of the conclusions regarding configuration are supported for the rigid bicyclic compound (−)-(9S)-9-phenyl-1,6-diazabicyclo[4.3.1]decan-7-one (15) by the X-ray crystal structure of the racemate.

Chromatographic enantiomer separation and circular dichroism spectra of chiral rhodanines

Rhodanines [2-thioxo-2,3-dihydro-1,3-thiazol-4(5H)-ones] with isopropyl, sec-butyl and neopentyl substituents in position 3 and methyl and phenyl substituents in position 5 have been resolved into enantiomers by chromatography on microcrystalline, swollen triacetylcellulose. While the 5-methyl compounds showed good optical stability, the 5-phenyl analogues underwent racemization in ethanol solution with half-lives of 1–2 h at ambient temperature and were therefore resolved at –3 °C.The UV spectra resemble those of N-acetyldithiocarbamates but with hypsochromic shifts because of the inclusion of the chromophore in a five-membered ring. Transition energies and absorption intensities were reasonably well reproduced by CNDO/S calculations.The CD spectra showed bands corresponding to the UV bands but also another band at ca. 260 nm, which may be ascribed to an n→π* transition located in the carbonyl group. The absolute configurations of the 5-methyl compounds were assigned on the basis of the signs of the n→π* bands, using Ripperger's quadrant rule for dithiocarbamates. The mechanisms for generation of rotational strengths in the 5-phenyl compounds are more complex and no safe assignments of absolute configurations could be made.The CD spectrum of 3-neopentyl-5-methylrhodanine in ethanol was found to be insensitive to the temperature from ambient to –97 °C, indicating a 1:1 equilibrium between the anti and syn forms, whereas the 5-phenyl analogue showed a considerable temperature dependence, indicating a more biased equilibrium.

Syntheses and CD studies of new cholesteno[4,3‐d]‐ and ‐[7,6‐d]pyrimidines

AbstractThe syntheses of 5α‐ and 5β‐cholest‐3‐eno[4,3‐d]pyrimidines (7) and (7′) could be achieved by using the hydroxymethylene derivative of cholestan‐4‐one (5) prepared from cholesterol (1). Their 2′‐derivatives 7a‐7d and 7′a‐7′c were also synthesized. 5α‐Cholest‐6‐eno[7,6‐d]pyrimidine (13) was prepared by the reaction of 5α‐cholestan‐7‐one (12) with tris‐(formylamino)methane. The CD spectra exhibit at least three Cotton effects between 300 and 210 nm, a first CD band around 290, a second one around 260, and a third one around 220 nm. An earlier developed quadrant rule can be applied to the determination of the sign of the first CD band, while the suggested helicity rule allows prediction of the third CD band.

Dicobalt hexacarbonyl derivatives of chiral acetylenes

Abstract ( μ 2 -RC 2 R′)Co 2 (CO) 6 complexes are prepared where R ≠ R′ and one of these substituents is a chiral organic group. The structures of the 11 complexes (10 new) range from the simplest possible chiral acetylenic hydrocarbon derivative (S-3-methyl-1-pentyne 1a ) to ethynylsteroid ( 1f, 1g, 1h ) and ethynylcodeine ( 1i, 1j, 1k ) derivatives. The CD spectra are reported and the results are analysed in terms of a quadrant rule. The CD spectra show that in all complexes the Co 2 (CO) 6 fragment of the molecule gets chirally perturbed. The reasons for the chiral perturbation include apolar repulsing (dominant for the hydrocarbon acetylenes) and polar attractive (“autosolvation”; dominant for acetylenes with polar hetero-atom containing substituents) forces.

Syntheses and CD studies of 5α‐cholesteno[3,2‐d]‐, ‐[2,3‐d]‐ and ‐[3,4‐d]pyrimidines

AbstractSyntheses of 5α‐cholesteno[3,2‐d]‐ (5a), [2,3‐d]‐ (12a), and [3,4‐d]pyrimidines (15a) have been achieved by using hydroxymethylene derivatives of relevant cholestanones prepared from cholesterol (1). Their CD spectra exhibit at least three Cotton effects between 300 to 200 nm, a first CD band around 290, a second one around 260 and a third one around 220 nm. A quadrant rule is developed and applied to the determination of the sign of the first CD band, while a helicity rule is applicable to the third CD band. The first band is positive in the [3,2‐d] series, whereas it is negative in the [2,3‐d] and the [3,4‐d] series. The third band is negative in all three series.

Experimental circular dichroism and VUV spectra of substituted oxiranes and thiiranes

Highly resolved circular dichroism spectroscopy of alkyl-substituted oxirane and thiirane chromophores was investigated in the vacuum ultraviolet region up to 9·0 eV (138 nm) using synchrotron radiation. Comparison of the gas phase and liquid phase spectra, along with results from theoretical calculations, could confirm the predicted Rydberg character of some excited states including their fine structures. The n(O)→R(3d) Rydberg transitions in chiral methyloxirane and the predicted n(S)→σ* valence transition of (S, S)-(−)-(2,3)-dimethylthiirane were detected for the first time. It could be shown that the quadrant rule for the first state previously verified for some chiral oxiranes also holds for (R)-(−)-1,2-epoxy-3-methyl-butane and (R)-(−)-1,2-epoxy-4-methyl-pentane and is found to be expandable for thiiranes. The first ns Rydberg transitions of dimethyloxirane could be fitted to a term formula.

Synthesis and CD spectral studies of some fused cholestenopyrimidines

Abstract

Chiroptical properties of C2-symmetric N-haloaziridines. Chiral rules for the N-haloaziridine chromophore

N-Chloro(a) and N-bromo (b) derivatives of C 2 -symmetricaziridines (2S,3S)-1-halogen-2,3-dimethylaziridines 1a,b and (2S,3S)-1-halogen-2,3-bis(alkoxycarbonyl)aziridines 2a,b and 3a,b were obtained. Haloaziridines 1a,b are an example of the «pure» N-haloaziridine chromophore which has the first Cotton effect (CE) in the region of 260-300 nm. A quadrant rule which connects the first CE sign with the stereochemical environment of the chromophore is offered. Haloaziridinecarboxylic esters are a specific case of the N-haloaziridine chromophore. The second CE sign at 220-230 nm in the CD spectra of these compounds obeys a reverse quadrant rule