Papers by Patrick Januel Mariano
Tetrahedron Letters, 1975
Separation Science, 1975
We have investigated the influence of the degree of cross-linking of Sephadex gels and the polari... more We have investigated the influence of the degree of cross-linking of Sephadex gels and the polarity of the eluent on the separation of cis- and trans-cinnamic acids and concluded that the physical basis for the separations is hydrophobic interactions between the solute and the cross-linkages in the gels.
Separation Science, 1976
Abstract Affinity chromatographic conditions have been developed that allow the separation of che... more Abstract Affinity chromatographic conditions have been developed that allow the separation of chemically modified α-chymotrypsins with reduced esterase activities compared to native α-chymotrypsin. This technique should be useful in purifying modified proteins having altered affinities for an affinity absorbent.
Journal of the Korean Chemical Society, 2010
In this account, three synthetic methodologies that serve as the basis for new strategies for the... more In this account, three synthetic methodologies that serve as the basis for new strategies for the preparation of selected natural products are briefly introduced. One process, involving ruthenium carbene catalyzed ring rearrangement metathesis developed by Grubbs and his coworkers, transforms alkene-tethered cycloalkenes to thermodynamically more favored alkene-tethered cycloalkenes. Another ruthenium carbene promoted reaction, referred to as dienyne metathesis, was uncovered in early studies by Grubbs and his collaborators. This process converts dienynes to fused bicyclic conjugated dienes. Finally, a novel photo-electrocyclization reaction of pyridinium salts, which leads to the formation of 4-aminocyclopenten-3,5-diol derivatives, is discussed. Examples are provided to show the utility of these methodologies in natural product synthesis. Emphasis is given to studies in which pyridinium salt photochemistry is coupled with ring rearrangement and dienyne metathesis in routes for the synthesis of polyhydroxyalted indolizidine alkaloids and the construction of the tricyclic core of the lepadiformine and cylindricine alkaloids.
Acta Crystallographica Section C Crystal Structure Communications, 1984
Bulletin of the Korean Chemical Society, 2013
This study explored a direct SET-photochemical strategy to construct a new family of thioene conj... more This study explored a direct SET-photochemical strategy to construct a new family of thioene conjugatednaphthalamide fluorophore based lariat-crown ethers which show strong binding properties towards heavy metal ions. Irradiations of designed nitrogen branched (trimethylsilyl)methylthio-terminated polyethylenoxytethered naphthalimides in acidic methanol solutions have led to highly efficient photocyclization reactions to generate naphthalamide based lariat type thiadiazacrown ethers directly in chemo-and regio-selective manners which undergo very facile secondary dehydration reactions during separation processes to produce their corresponding amidoenethio ether cyclic products tethered with electron donating diethyleneoxy-and diethyenethio-side arm chains. Fluorescence and metal cation binding properties of the lariat type enamidothio products were examined. The photocyclized amidoenethio products, thioene conjugated naphthalamide fluorophore containing lariat-thiadiazacrowns exhibited strong fluorescence emissions in region of 330-450 nm along with intramolecular exciplex emissions in region of 450-560 nm with their maxima at 508 nm. Divalent cation Hg 2+ and Pb 2+ showed strong binding to sulfur atom(s) in side arm chain and atoms in enethiadiazacrown ether rings which led to significant enhancement of fluorescence from its chromophore singlet excited state and concomitant quenching of exciplex emission. The dual fluorescence emission responses towards divalent cations might provide a new guide for design and development of fluorescence sensors for detecting those metals.
Studies conducted during the grant period concentrated on two aspects of the problems proposed fo... more Studies conducted during the grant period concentrated on two aspects of the problems proposed for investigation. First strategies for selection of organic systems of potential utility in solar energy storage and conversion methodologies were outlined. Several criteria for judging the solar to thermal energy conversion efficiency, energy storage capacity, and quality of retrievable heat were developed for systems operating on the basis of the reversible cyclie A reversible B, in which the forward reaction (A ..-->.. B) is given photochemically and the reverse (B ..-->.. A) using catalysts. The criteria established to evaluate these systems have been applied to the familiar norbornadiene - quadricyclene cycle. The second phase of the investigation conducted during the project period has involved laboratory experiments on a new class of potentially important energy storing photoreactions involving the reversible isomerization of 1-substituted-2-pyridones. These materials undergo electrocyclic closure upon irradiation to produce the kinetically stable Dewarpyridones. Several of the other important features of this system which appears to make it ideally suited for application in solar energy storage and conversion technologies are outlined. In addition, the results of our initial exploratory efforts on these compounds are summarized. Studies demonstrated that simple 2-pyridones possessing vinyl substituents on nitrogenmore » have alternate excited state reaction pathways available leading to the production of oxazolopyridinium yields. A complete kinetic analysis of these processes as well as a survey of solvent polarity and substituent effects of reaction efficiencies have been performed and are outlined.« less
Phosphonoacetaldehyde hydrolase (PAH) catalyzes the hydrolysis of the P-C bond in phosphonoacetal... more Phosphonoacetaldehyde hydrolase (PAH) catalyzes the hydrolysis of the P-C bond in phosphonoacetaldehyde (PA) to yield P/sub i/ and acetaldehyde (AA). The enzyme requires MgS and is inactivated by NaBH4 in the presence of PA. The mechanism of PAH may be analogous to the US -ketodecarboxylases in which Mg may activate the substrate for bond cleavage or in which a Schiff
Reviews of Chemical Intermediates, 1981
Tetrahedron Letters, 1980
Photocycloadditionsofthe electron poor olefins, acrylonitrile and methyl acrylate to a series of ... more Photocycloadditionsofthe electron poor olefins, acrylonitrile and methyl acrylate to a series of para-substituted 2-phenyl-1-pyrrolinium pet-chlorates have been explored as part of studies designed to test new synthetic methods. Studies in our laboratory3 have uncovered interesting olefin photoadditions to iminium salts occuring through electron-transfer or 2+2-cycloaddition pathways. Additions of electron poor olefins to 2-phenyl-1-pyrrolinium perchlorate (l_H+zH) appear to involve initial 2+2-cycloaddition across the C-l C-Z n-bond of the aromatic ring (/H-*?H) followed by ring expansion and aromatization.3b This reaction appears potentially applicable to the synthesis of spirocyclic amines, exemplified by the proposed route to serratinine4 4 outlined retrosynthetically in Chart 1. The success of this approach would depend upon the effect of aromatic ring substitution, needed for spiroannulation and A-ring functional group introduction, on photoaddition. In order to investigate this point, we have studied photocycloadditions of electron poor olefins and a series of Z-p-substituted-phenyl pyrrolinium perchlorates 1. The 1-pyrroline precursors of l_F, lC1, 1CH31 l,Br and 101ZH3,~ were prepared by use of the method of Bielawski 6. involving addition of the corresponding aryl lithium to N-vinylpyrrolidone followed by hydrolysis. Irradiations7 were conducted on methanolic acrylonitrile or methyl acrylate solutions (1 M) of the salts (ca. 10m3-M), formed in situ from the pyrrolines and 70%-HC104. Crude photolysates were neutralized, concentrated, and products purified by molecular distillation and/or chromatography. Yields of the benzospirocyclic amines produced are recorded in Table 1. 9 Product structures were assigned on the basis of spectroscopic data and comparisons with that for the known parent amines, 3CN-H and 3C0 CH-H. 3b-2 3 Chemical correlations of ZCN-Cl and 3CN-Br with ?CN-H (LiA1H4 THF, 6O"C, 12h-reduction to identical mixtures of the stereoisomerit diamines 6) provided unambiguous structural assignments to these materials. The results indicate that additions of electron poor olefins to photo-excited Z-aryl-lpyrrolinium perchlorates, proceeding by initial 2+2 cycloaddition to the aromatic ring, serve as useful methods for construction of the reasonably complex benzospirocyclic amines. An exception to this generality was found in studies of the Z-anisyl-1-pyrrolinium salt, lOCH3. The spirocyclic amines obtained by cycloaddition to p-alkoxy substituted salts would be ideal precursors to the phenoxides 5, useful in Spiro-annulation procedures (Chart 1). Irradiation of methanolic solutions of lOCH3 and acrylonitrile leads to generation of an abnormal photoadduct [. Spectroscopic data indicate that this material is a 1:l adduct containing a e-disubstituted aromatic ring and a 1,2,2-trisubstituted pyrrolidine unit and suggest that it possesses the bicyclic azetidine structure, 7. 1 The characteristic ABM pattern observed in the H-NMR spectrum lo is that expected for a conformationally fixed CH2CH(NR2)CN moiety.
Alkaloids: Chemical and Biological Perspectives, 1992
ABSTRACT Members of the yohimbine alkaloid family possess a characteristic penta-cyclic indole sk... more ABSTRACT Members of the yohimbine alkaloid family possess a characteristic penta-cyclic indole skeleton 1. Representative compounds in this family include the Rauwolfia alkaloids, such as reserpine (2) and deserpidine (3), and the yohimbines (4–9). These compounds exhibit a wide range of medicinal properties (1,2).
Tetrahedron, 2015
In the current study, 1,2-diarylpropan-1,3-diols, containing varying numbers of methoxy substitue... more In the current study, 1,2-diarylpropan-1,3-diols, containing varying numbers of methoxy substituents that mimic b-1 type units in lignins, were prepared and subjected to photochemical and enzymatic SET oxidative CeC bond cleavage reactions to explore how product distributions and reactivity profiles depend on the numbers and positions of arene ring methoxy-substituents. For this purpose, product distributions of SET-promoted photochemical reactions of the b-1 model compounds and the characteristics of lignin peroxidase catalyzed bond cleavage reactions of these substances were explored. The results show that both the photochemical and enzymatic reactions, which are known to occur by initial SET to form arylpropanoid cation radicals, generate predominantly aldehydes and b-hydroxyketones through cation radical C1eC2 bond cleavage pathways. In addition, analysis of the relative quantum efficiencies of the SET photochemical processes shows that they do not depend greatly on the numbers and positions of arene ring methoxy substituents of the b-1 model compounds.
Tetrahedron Letters, 1974
In the course of our recent investigations of potential rearrangement reactions related to the me... more In the course of our recent investigations of potential rearrangement reactions related to the methylideneoxirane to cyclopropanone transformation,l we have had to develop methods for preparation of alkylidene-2,3_dihydrofurans of general structure ,_l,. We would like to report here the observation of an abnormal reaction which leads to the formation of a C"2 stable derivative of 1 and offers the potential of being a general route to this sparsely studied series of compounds.2
ChemInform, 2003
Two important types of α-heterolytic fragmentation reactions of aminium radicals are discussed. I... more Two important types of α-heterolytic fragmentation reactions of aminium radicals are discussed. In these fragmentation processes, transfer of electrofugal groups from the aminium radicals to either Lowry-Bronsted or Lewis bases produces α-amino radicals. The results of recent studies that provided key information about the dynamics of the important aminium radical fragmentation reactions, deprotonation, desilylation, are summarized. Finally, selected examples, which demonstrate how knowledge of the relative rates of aminium radical cleavage can be used to design synthetically relevant SET-promoted photocyclization reactions, are presented.
ChemInform, 2008
Amino acids U 0400 Observations Made in Exploring a Pyridinium Salt Photochemical Approach to the... more Amino acids U 0400 Observations Made in Exploring a Pyridinium Salt Photochemical Approach to the Synthesis of (+)-Lactacystin.-The key step in the synthesis of (+)-lactacystin (V), a biologically interesting proteasome inhibitor, involves photocyclization of a cyclopenta-fused pyridinium salt using the newly synthesized compound (I) as model substrate. Especially the stereoselective formation of the tricyclic carbamate (IV) is described as potentially compatible with the general strategy.
Synthetic Organic Photochemistry, 1984
The major applications of organic photochemical processes to synthetic problems have to date focu... more The major applications of organic photochemical processes to synthetic problems have to date focused for the most part on the use of photocycloadditions and electrocyclizations in the preparation of strained ring compounds in target systems or key synthetic intermediates. The utility of these methods in selected preparative sequences for construction of natural and/or theoretically interesting products has been reviewed.(1) In general, these excited-state reactions share several unique features which make their utility in synthetic chemistry particularly advantageous. For example, photocycloadditions serve as useful methods for generating carbon-carbon bonds in strained ring systems which, due to their high energy content, are capable of participating in facile ring cleavage processes leading to desired intermediates. Similarly, electrocyclizations lead to the installation of difficultly prepared cyclic units from more readily available acyclic precursors. The applications of these reactions to synthetic problems is further broadened by their predictable regiochemical and stereochemical courses utilizing simple molecular orbital methods. Other classes of excited-state reactions have been used for the introduction and interconversion of functionality in molecular systems. Thus, several classes of photochemical processes appear compatible with the criteria established for evaluation of synthetically useful gound-state transformations.
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Papers by Patrick Januel Mariano