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1.
Isotachysterol, the acid-catalyzed isomerization product of vitamin D3, produces seven previously unknown oxygenation products in a self-initiated autoxidation reaction under atmospheric oxygen in the dark at ambient temperature. They are (5R)-5,10-epoxy-9,10-secocholesta-6,8(14)-dien-3β-ol (6a), (5S)-5,10-epoxy-9,10-secocholesta-6,8(14)-dien-3β-ol (6b), (10R)-9,10-secocholesta-5,7,14-trien-3β,10-diol (7a), (10S)-9,10-secocholesta-5,7,14-trien-3β,10-diol (7b), (7R,10R)-7,10-epoxy-9,10-secocholesta-5,8(14)-dien-3β-ol (8), 5,10-epidioxyisotachysterol (9) and 3,10-epoxy-5-oxo-5,10-seco-9,10-secocholesta-6,8(14)-dien-10-ol (10). The formation of these products is explained in terms of free radical peroxidation chemistry. 相似文献
2.
New PHOX ligands, derived in three steps from (1R,2S,3R,5R)-3-amino-apopinan-2-ol 1 and (1R,2R,3S,5R)-3-amino-pinan-2-ol 2 were applied as chiral ligands for the formation of ruthenium catalysts. The catalysts were used in asymmetric transfer hydrogenations of prochiral ketones producing the corresponding alcohols in moderate to high yields and enantioselectivity. 相似文献
3.
《Tetrahedron》1986,42(6):1763-1768
(-)-(1S,3S,5R,6S,8R,10R)-Trishomocubanethanoic acid (5) of known absolute configuration and absolute rotation was converted into (+)-(1S,3S,5S,6S,8R,10R)-2-bromoethynyl-D3-trishomocubane (27) of C3 symmetry. 1,3,5,7-Tetraethynyladamantane (22), with Td symmetry, was prepared from 1,3,5,7-tetrakis(hydroxymethyl)adamantane(13). Coupling of the C3-component 27 with the Td component 22 was successfully accomplished by Chodkiewicz and Cadiot's procedure providing (+)-1,3,5,7-tetrakis[2-(1S,3S,5R,6S,8R,10R)-D3-trishomocubanylbuta-1,3-diynyl]adamantane(4) whose highest attainable static and time-averaged dynamic symmetry are T and (C3)4 XXX T,respectively. 相似文献
4.
This paper reports the synthesis, characterization and electronic circular dichroism (ECD) spectroscopic studies of a new type of crown ethers and their achiral analogues containing a tetrahedral phosphorous centre. The synthetic routes to the two chiral phosphinate derivatives [(R,R)-10 and (R,R)-11] were similar, starting from the earlier reported ethyl bis(2-hydroxyphenyl)phosphinate and the unreported methyl bis(2-hydroxyphenyl)phosphinate, respectively. The enantiopure crown ether containing phosphinic acid unit (R,R)-14 was obtained by hydrolysis of the phosphinates (R,R)-10 and (R,R)-11, respectively. ECD spectroscopy was used for investigation of the chiroptical properties as well as complex formation ability of the novel enantiopure ligands. Owing to the presence of the aryl substituents the ECD spectra are rich in bands in the 1Bb, 1La and 1Lb regions (190-250 nm and 260-330 nm, respectively). In the case of (R,R)-14, a solvent dependent conformational behaviour was observed due to the strong dimer or aggregate forming ability of the POOH groups. This finding was supported by theoretical calculation of the monomer and the dimer forms. Phosphinates (R,R)-10 and (R,R)-11 form complexes with α-phenylethylammonium perchlorate (PEA) and α-(1-naphthyl)ethyl ammonium perchlorate (NEA) but do not discriminate between their enantiomers. All three chiral crown ethers bind strongly cations of ionic radii <∼1 Å. 相似文献
5.
(−)-α-Bisabolol, a bioactive monocyclic sesquiterpene alcohol, has been used in pharmaceutical and cosmetic products with anti-inflammatory, antibacterial and skin-caring properties. However, the poor water solubility of (−)-α-bisabolol limits its pharmaceutical applications. It has been recognized that microbial transformation is a very useful approach to generate more polar metabolites. Fifteen microorganisms were screened for their ability to metabolize (−)-α-bisabolol in order to obtain its more polar derivatives, and the filamentous fungus Absidia coerulea was selected for scale-up fermentation. Seven new and four known metabolites were obtained from biotransformation of (−)-α-bisabolol (1), and all the metabolites exhibited higher aqueous solubility than that of the parent compound 1. The structures of newly formed metabolites were established as (1R,5R,7S)- and (1R,5S,7S)-5-hydroxy-α-bisabolol (2 and 3), (1R,5R,7S,10S)-5-hydroxybisabolol oxide B (4), (1R,7S,10S)-1-hydroxybisabolol oxide B (5), 12-hydroxy-α-bisabolol (7), (1S,3R,4S,7S)- and (1S,3S,4S,7S)-3,4-dihydroxy-α-bisabolol (8 and 10) on the basis of spectroscopic analyses. These compounds could also be used as reference standards for the detection and identification of the metabolic products of 1 in the mammalian system. 相似文献
6.
The thermolysis of (3R,9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindole-3-carboxylic acids in Ac2O led to novel 3-methylene-2,5-dioxo-3H,9bH-oxazolo[2,3-a]isoindoles and chiral (9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindoles were obtained on FVP. Starting from l-cysteine methyl ester (3R,10bR)-5-oxo-2,3-dihydro-10bH-[1.3]thiazolo[3,2-c][1,3]benzoxazines were obtained as single stereoisomers. The thermolysis of (3R,10bR)-5-oxo-2,3-dihydro-10bH-[1.3]thiazolo[3,2-c][1,3]benzoxazine-3-carboxylic acid in Ac2O gave 5-acetyl-2-phenyl-2,3-dihydrothiazole. The structures of methyl (3R,9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindole-3-carboxylate 1a and methyl (2R,4R)-N-chlorocarbonyl-2-(2-hydroxyphenyl)thiazolidine-4-carboxylate 9 were determined by X-ray crystallography. 相似文献
7.
V. A. Mamedov A. M. Murtazina L. P. Sysoeva E. V. Mironova Sh. K. Latypov A. A. Balandina S. F. Kadyrova A. T. Gubaidullin I. A. Litvinov 《Russian Journal of Organic Chemistry》2008,44(6):916-920
Condensation of diethyl 2,4,6-trioxoheptanedioate with 4-methoxy-2-(4-methylphenyliminomethyl)-phenol in acetone gave diethyl 5-hydroxy-9-methoxy-1-(4-methylphenyl)-4-oxo-1,4a,5,10b-tetrahydro-4Hchromeno[ 4,3-b]pyridine-2,5-dicarboxylate as a mixture of diastereoisomers. The major (4aR,5R,10aR)-isomer was isolated as individual substance, and its structure was proved by X-ray analysis. 相似文献
8.
Amanda C FergusonRobert M Adlington Domnic H MartyresPeter J Rutledge Andrew CowleyJack E Baldwin 《Tetrahedron》2003,59(41):8233-8243
A route has been developed which allows synthesis of novel cyclobutanone analogues of penicillin. This is illustrated by the synthesis of (1R,4R,5R,5′R,7S)-(1b) and (1S,4S,5S,5′R,7R)-7-[5′-amino-5′-carboxy]pentanamido]-2-thiabicyclo[3.2.0]heptan-6-one-4-carboxylate (1a), an analogue of penicillin N. The key steps in the synthesis were the formation of the bicyclic structure via a [2+2] cycloaddition and the introduction of nitrogen at C7 via an intramolecular nitrene insertion. 相似文献
9.
Christof Kratky Wolfgang Reischl Elisabeth Altmann Erich Zbiral 《Monatshefte für Chemie / Chemical Monthly》1982,113(4):439-448
Oxidation of the α- and β-4-phenyl-1,2,4-triazolin-3,5-dione adducts of vitamin D3 (2 and1) withMCPBA yields two diastereomeric mixtures of the (5,10)-(7,8)-dioxiranes3 a,3 b,3 c and4 a,4 b respectively. The corresponding benzoates5 a,5 b,6 a and6 b were prepared and the X-ray crystal structure of5 b was determined. This analysis proved5 b to be the (5R, 1 OS)-(7R, 8R)-dioxirane of the β-resp. (6S)-4-phenyl-1,2,4-triazolin-3,5-dione adduct1 of vitamin D3. 相似文献
10.
MiraS. Bjelakovi LjubinkaB. Lorenc VladimirD. Pavlovi Bernard Tinant Jean‐Paul Declercq Jaroslav Kalvoda 《Helvetica chimica acta》2003,86(6):2121-2135
Oxidations of 5α‐hydroxy‐B‐norcholestan‐3β‐yl acetate ( 8 ) with Pb(OAc)4 under thermal or photolytic conditions or in the presence of iodine afforded only complex mixtures of compounds. However, the HgO/I2 version of the hypoiodite reaction gave as the primary products the stereoisomeric (Z)‐ and (E)‐1(10)‐unsaturated 5,10‐seco B‐nor‐derivatives 10 and 11 , and the stereoisomeric (5R,10R)‐ and (5S,10S)‐acetals 14 and 15 (Scheme 4). Further reaction of these compounds under conditions of their formation afforded, in addition, the A‐nor 1,5‐cyclization products 13 and 16 (from 10 ) and 12 (from 11 ) (see also Scheme 6) and the 6‐iodo‐5,6‐secolactones 17 and 19 (from 14 and 15 , resp.) and 4‐iodo‐4,5‐secolactone 18 (from 15 ) (see also Scheme 7). Oxidations of 5β‐hydroxy‐B‐norcholestan‐3β‐yl acetate ( 9 ) with both hypoiodite‐forming reagents (Pb(OAc)4/I2 and HgO/I2) proceeded similarly to the HgO/I2 reaction of the corresponding 5α‐hydroxy analogue 8 . Photolytic Pb(OAc)4 oxidation of 9 afforded, in addition to the (Z)‐ and (E)‐5,10‐seco 1(10)‐unsaturated ketones 10 and 11 , their isomeric 5,10‐seco 10(19)‐unsaturated ketone 22 , the acetal 5‐acetate 21 , and 5β,19‐epoxy derivative 23 (Scheme 9). Exceptionally, in the thermal Pb(OAc)4 oxidation of 9 , the 5,10‐seco ketones 10, 11 , and 22 were not formed, the only reaction being the stereoselective formation of the 5,10‐ethers with the β‐oriented epoxy bridge, i.e. the (10R)‐enol ether 20 and (5S,10R)‐acetal 5‐acetate 21 (Scheme 8). Possible mechanistic interpretations of the above transformations are discussed. 相似文献
11.
The solvolysis of (Z)- and (E)-3β-acyloxy-5,10-seco-1(10)-cholesten-5β-ol p-nitrobenzoates 4 and 5 has been investigated and compared with the solvolytic reactivity of the epimeric (Z)- and (E)-5α-p-nitrobenzoates 1 and 2, as well as of the reference compound, i.e. the 1,10-saturated 5α-p-nitrobenzoate. Kinetic data and product analysis revealed that the relative spatial orientation of the 1(10)-olefinic double bond and the chiral center at C(5) in the 10-membered ring, which these secosteroidal 5-p-nitrobenzoates can adopt in the transition state, is the main factor which determines their solvolytic behaviour, so that the esters 1,2 and 5 solvolyse with transannular double bond participation, while such an interaction is not present in the case of the (Z)-5β-ester 4. 相似文献
12.
Dibenz[b, f,-1]azapentalene dianion (3) was allowed to react with N,N diethyl - O - mesitylenesulfonylhydroxylamine (4) in order to obtain N,N - diethyl - 5,10 - dihydroindeno[1,2 - b] - indol - 10 - amine (11). The available data indicated that electron transfer processes were involved in the formation of 11. Attempts to obtain dibenz[b, f,-1]azapentalene (1) and 11 by Hofman elimination or by the reaction of 11 with trifluoroacetic acid were unsuccessful. 相似文献
13.
《Tetrahedron: Asymmetry》2007,18(18):2218-2226
The trans-configured fosfomycin analogue, diethyl (1S,2S)-1,2-epoxy-3-hydroxypropylphosphonate, was synthesised by the intramolecular Williamson reaction of diethyl (1S,2R)-1,3-dihydroxy-2-mesyloxypropylphosphonate. The cis-analogue was obtained as O-ethyl or O,O-diethyl (1R,2S)-1,2-epoxy-3-hydroxypropylphosphonates, when (1R,2R)-1,3-dihydroxy-2-mesyloxypropylphosphonate or its 3-O-trityl derivative were used as starting materials, respectively. The intramolecular Williamson cyclisations of diethyl (1S,2R)- and (1R,2S)-1-benzyloxy-3-hydroxy-2-mesyloxypropylphosphonates led to diethyl (1S,2S)- and (1R,2S)-2,3-epoxy-1-benzyloxypropylphosphonates, respectively, with the concomitant formation of diethyl (E)-1-benzyloxy-3-hydroxyprop-1-en-1-phosphonate. From diethyl (1S,2S)- and (1R,2S)-2,3-epoxy-1-benzyloxypropylphosphonates, enantiomerically pure diethyl (1S,2S)- and (1R,2S)-1,2-dihydroxypropylphosphonates were obtained by catalytic hydrogenation, while diethyl (1S,2S)- and (1R,2S)-3-acetamido-1,2-dihydroxypropylphosphonates were produced after epoxide ring opening with dibenzylamine, acetylation and hydrogenolysis. 相似文献
14.
R. V. Shafikov A. Yu. Spivak V. N. Odinokov 《Russian Journal of Organic Chemistry》2011,47(2):290-294
Based on the catalyzed by lipase Amano PS kinetic separation of the two-component mixture of diastereomers of (2RS,6R,10R)-6,10,14-trimethylpentadecan-2-ol in the acylation with the succinic anhydride we obtained the (2R,6R,10R)-6,10,14-trimethylpentadecan-2-ol, the sex pheromone of rice moth (Corcyra cephalonica) and its (2S,6R,10R)-diastereomer. 相似文献
15.
Jhillu S. Yadav Kamakolanu Uma Gayathri Neetipalli Thrimurtulu Attaluri R. Prasad 《Tetrahedron》2009,65(17):3536-1547
The stereoselective synthesis of (10R,14R)-10,14-dimethyloctadec-1-ene (1), (5R,9R)-5,9-dimethyloctadecane (2), and (5R,9R)-5,9-dimethylheptadecane (3) the sex pheromone components of female apple leafminer was accomplished by reductive elimination tosyl and isonitrile groups of dialkylated tosylmethyl isonitrile. The key steps involved were dialkylation of TosMIC with 1-iodo 2-methyl alkanes, which were derived from Evan's alkylation of chiral auxiliary and subsequent reduction. 相似文献
16.
Katarína Kadle?íková Vincent Dalla Štefan Marchalín Bernard Decroix 《Tetrahedron》2005,61(20):4743-4754
A diastereoselective synthesis of two new swainsonine's analogues 1a and 1b with the piperidine ring fused to a phenyl nucleus at C6-C7, namely (1R, 2S, 10R, 10aR)-(+)-1,2,10-trihydroxy-1,2,3,5,10,10a-hexahydrobenzo[f] indolizine (1a) and (1S, 2R, 10R, 10aR)-(+)-1,2,10-trihydroxy-1, 2, 3, 5, 10, 10a-hexahydrobenzo[f] indolizine (1b), is described. Throughout this work, the effectiveness of the tricyclic indolizidine dione 5, readily available in three steps from the cheap l-glutamic acid, as an attractive platform for chemo- and stereodivergent transformations is illustrated. The key steps involved totally diastereoselective ketone reduction of compound 5 and catalytic cis-dihydroxylation of the unsaturated amide 10. The synthetic strategy also allowed for the diastereoselective synthesis of benzoanalogues of the 1,8a-di-epi-lentiginosine 3a ((1R, 2S, 10aR)-(+)-1,2-dihydroxy-1, 2, 3, 5, 10, 10a-hexahydrobenzo[f]indolizine) and 2,8a-di-epi-lentiginosine 3b ((1S, 2R, 10aR)-(+)-1,2-dihydroxy-1,2,3,5,10,10a-hexahydrobenzo[f]indolizine). 相似文献
17.
《Tetrahedron: Asymmetry》2006,17(7):1023-1026
The reduction of α- or β-ketophosphonates with a chiral reactant 1, prepared from sodium borohydride and (R)- or (S)-tartaric acids, led to the formation of both (S)- and (R)-α- or β-hydroxyphosphonates in high yields. The stereoselectivity of the reaction depended on the absolute configurations of 1 and the ketophosphonates. The reduction of di(1R,2S,5R)-menthyl ketophosphonates with (R)-1 proceeded with matched double asymmetric induction to give high diastereomeric excesses of hydroxyphosphonates (up to 96% de). This methodology was used for the preparation of enantiomerically pure phosphonate modified carnitine on a multigram scale. 相似文献
18.
Frank Kienzle 《Helvetica chimica acta》1980,63(3):563-567
Note on the Synthesis of (E)-12-Hydroxy-10-heptadecenoic Acid, (5E, 10E)-12-Hydroxy-5, 10-heptadienoic Acid and (5Z, 10E)-12-Hydroxy-5,10-heptadienoic Acid The syntheses of two heptadecadienoic and one heptadecenoic acid, compounds which formally may be derived from prostaglandin-like molecules by removal of a C3-fragment from the five-membered ring, are described. 相似文献
19.
A full account of the novel and flexible approach to hydroxylated 8-azabicyclo[3,2,1]octan-3-ones and 9-azabicyclo[3,3,1]nonan-3-ones is presented.Using keto-lactams as the starting materials,this two-step method consists of silyl enol ether formation with TBDMSOTf,lactam activation with Tf2O/DTBMP,and halide-promoted cyclization.Radical dechlorination of the resulting 1-halotropan-3-ones led to the corresponding hydroxylated tropan-3-ones,which can be hydrogenated to yield3,6-dihydroxytropanes.Starting from optically active keto-lactams,the method has been applied to the enantioselective syntheses of(+)-(1S,3S,5R,6S)-pervilleine C(6),(+)-(1S,3R,5S,6R)-valeroidine(3),(+)-(1S,3S,5R,6S)-dibenzoyloxytropane(8),and(+)-(1S,3S,5R,6S)-merredissine(9). 相似文献
20.
Biswanath Das Boyapati Veeranjaneyulu Penagaluri Balasubramanyam Malampati Srilatha 《Tetrahedron: Asymmetry》2010,21(23):2762-2767
The stereoselective total synthesis of two naturally occurring α-pyrone derivatives, (+)-strictifolione and (6R)-6[(E,4R,6R)-4,6-dihydroxy-10-phenyl-1-decanyl]-5,6-dihydro-2H-2-pyrone has been accomplished involving the Sharpless kinetic resolution and olefin cross-metathesis as the key reactions. 相似文献