Spectroscopic and structural investigation on intermediates species structurally associated to the tricyclic bisguanidine compound and to the toxic agent, saxitoxin

Romani, Davide; Tsuchiya, Shigeki; Yotsu‐Yamashita, Mari; Brandán, Silvia Antonia

doi:10.1016/j.molstruc.2016.04.039

Cited by 27 publications

(20 citation statements)

References 48 publications

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“…Here, the assignments oh three species were performed considering the corresponding normal internal coordinates, transferable scaling factors and only contributions ≥ 10%. In addition, the frontier orbitals and some remarkable descriptors were used to predict reactivities and behaviours of three species [31][32][33][34][35][36][37][38][39][40][41]. The predicted Raman spectra in activities were converted to intensities for a better correlation with the experimental one [42,43].…”

Section: Methodsmentioning

confidence: 99%

Structural and vibrational studies of equilenin, equilin and estrone steroids

2019

Biointerface Res Appl Chem

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Three species associated with estrogens have been studied in this work, equilenin, equilin and estrone. Their molecular structures have been theoretically studied in gas phase with the hybrid B3LYP/6-31G* method. NBO, AIM and frontier orbital calculations were computed for the three species at the same level of theory. Higher dipole moment and volume were observed for estrone while equilin presents higher volume than equilenin but lower dipole moment value. Probably, the unsaturated C=C in the B ring of equilin could explain those differences. The differences observed in the properties could be clearly explained by differences in the dihedral angles. The analyses of MK and Mulliken charges evidence the higher variations on the C atoms common to the B, C and D rings in the three species. The mapped MEP surfaces show that both A and B rings of equilenin are different from the other ones because they have aromatic naphthalene core, as was evidenced experimentally. The NBO studies support the higher stability of equilin, in relation to equilenin and estrone while the AIM analyses reveal the higher stability for estrone. The gap values suggest that equilenin is the most reactive species due to its higher global electrophilicity value, in agreement with the higher stability observed for this species while the higher global nucleophilicty values are observed for equilin and estrone. Here, the harmonic force fields, scaled force constants and the complete assignments of 108, 114 and 120 vibration modes for equilenin, equilin and estrone, respectively are reported for first time.

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Section: Methodsmentioning

confidence: 99%

Structural and vibrational studies of equilenin, equilin and estrone steroids

2019

Biointerface Res Appl Chem

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“…We have also approached the elucidation of STX biosynthesis on the basis of biosynthetic intermediates identified by LC-MS analysis as well as synthesis.I no ur previous studies, we chemically synthesized the genetically predicted biosynthetic intermediates of the early stage,namely,Int-A' (3)and Int-C'2( 4), and identified them in the PST-producing cyanobacterium Anabaena circinalis (TA04) [8c] and the dinoflagellate Alexandrium tamarense (Axat-2) [14] by using LC/ MS. [15] We also identified Cyclic-C' (5)a st he first shunt product in STX biosynthesis,d erived from Int-C'2( 4). [16][17][18] Moreover,i ncorporation experiments using [ 15 N 2 ]Int-A' (3' ') and [ 15 N 2 ]Int-C'2( 4' ')p roved that these compounds are genuine precursors of the PSTs C1 (6)a nd C2 (7), which are epimers at C11. [18] However,the pathway from 4 to PSTs, including the construction of the tricyclic skeleton of STX, remained unknown ( Figure 1).…”

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confidence: 99%

Synthesis and Identification of Key Biosynthetic Intermediates for the Formation of the Tricyclic Skeleton of Saxitoxin

et al. 2017

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Saxitoxin (STX) and its analogues are potent voltage-gated sodium channel blockers biosynthesized by freshwater cyanobacteria and marine dinoflagellates. We previously identified genetically predicted biosynthetic intermediates of STX at early stages, Int-A' and Int-C'2, in these microorganisms. However, the mechanism to form the tricyclic skeleton of STX was unknown. To solve this problem, we screened for unidentified intermediates by analyzing the results from previous incorporation experiments with N-labeled Int-C'2. The presence of monohydroxy-Int-C'2 and possibly Int-E' was suggested, and 11-hydroxy-Int-C'2 and Int-E' were identified from synthesized standards and LC-MS. Furthermore, we observed that the hydroxy group at C11 of 11-hydroxy-Int-C'2 was slowly replaced by CD O in CD OD. Based on this characteristic reactivity, we propose a possible mechanism to form the tricyclic skeleton of STX via a bicyclic intermediate from 11-hydroxy-Int-C'2.

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“…In our previous studies, we chemically synthesized the genetically predicted biosynthetic intermediates of the early stage, namely, Int‐A′ ( 3 ) and Int‐C′2 ( 4 ), and identified them in the PST‐producing cyanobacterium Anabaena circinalis (TA04) and the dinoflagellate Alexandrium tamarense (Axat‐2) by using LC/MS . We also identified Cyclic‐C′ ( 5 ) as the first shunt product in STX biosynthesis, derived from Int‐C′2 ( 4 ) . Moreover, incorporation experiments using [ 15 N 2 ]Int‐A′ ( 3′ ) and [ 15 N 2 ]Int‐C′2 ( 4′ ) proved that these compounds are genuine precursors of the PSTs C1 ( 6 ) and C2 ( 7 ), which are epimers at C11 .…”

Section: Figurementioning

confidence: 99%

Synthesis and Identification of Key Biosynthetic Intermediates for the Formation of the Tricyclic Skeleton of Saxitoxin

et al. 2017

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Saxitoxin (STX) and its analogues are potent voltage‐gated sodium channel blockers biosynthesized by freshwater cyanobacteria and marine dinoflagellates. We previously identified genetically predicted biosynthetic intermediates of STX at early stages, Int‐A′ and Int‐C′2, in these microorganisms. However, the mechanism to form the tricyclic skeleton of STX was unknown. To solve this problem, we screened for unidentified intermediates by analyzing the results from previous incorporation experiments with 15N‐labeled Int‐C′2. The presence of monohydroxy‐Int‐C′2 and possibly Int‐E′ was suggested, and 11‐hydroxy‐Int‐C′2 and Int‐E′ were identified from synthesized standards and LC‐MS. Furthermore, we observed that the hydroxy group at C11 of 11‐hydroxy‐Int‐C′2 was slowly replaced by CD3O in CD3OD. Based on this characteristic reactivity, we propose a possible mechanism to form the tricyclic skeleton of STX via a bicyclic intermediate from 11‐hydroxy‐Int‐C′2.

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Spectroscopic and structural investigation on intermediates species structurally associated to the tricyclic bisguanidine compound and to the toxic agent, saxitoxin

Cited by 27 publications

References 48 publications

Structural and vibrational studies of equilenin, equilin and estrone steroids

Structural and vibrational studies of equilenin, equilin and estrone steroids

Synthesis and Identification of Key Biosynthetic Intermediates for the Formation of the Tricyclic Skeleton of Saxitoxin

Synthesis and Identification of Key Biosynthetic Intermediates for the Formation of the Tricyclic Skeleton of Saxitoxin

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