Highly Regioselective 3-Hydroxyalkylations of Boron 4-Methoxy-2-furanolates: A New Entry to 5-Unsubstituted and 5-Monosubstituted 3-Acyl-4-O-Methyl Tetronates

Paintner, Franz F.; Allmendinger, Lars; Bauschke, Gerd

doi:10.1055/s-2001-18071

Cited by 20 publications

(10 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[4][5][6] More recently, we have introduced the chelation-controlled C-3 selective hydroxyalkylation of boron 4-methoxy-2-furanolates 4 with aldehydes leading to 3-acyl tetronates after oxidation of the intermediate alcohols. 7 This method, however, although highly regioselective and good yielding, is essentially restricted to aliphatic aldehydes and thus limited in scope.…”

mentioning

confidence: 99%

“…This is particularly remarkable, since product 1g had hardly been accessible with our previously reported boron furanolate-based 3-hydroxyalkylation method. 7 3-(1-Hydroxyalkyl) tetronates, e.g. 1g, are known to be readily oxidized with various reagents such as IBX 7 or MnO 2 16 to give the corresponding 3-acyl tetronates.…”

mentioning

confidence: 99%

“…7 3-(1-Hydroxyalkyl) tetronates, e.g. 1g, are known to be readily oxidized with various reagents such as IBX 7 or MnO 2 16 to give the corresponding 3-acyl tetronates. However, 3-acyl tetronates are also directly accessible from intermediates 5 by reaction with acid chlorides at -78°C (entry 9).…”

mentioning

confidence: 99%

See 2 more Smart Citations

A General Method for the Highly Regioselective Introduction of Substituents into the 3-Position of 5-Unsubstituted 4-O-Alkyl Tetronates

Paintner¹,

Allmendinger²,

Bauschke³

2005

Synlett

Self Cite

View full text Add to dashboard Cite

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

A General Method for the Highly Regioselective Introduction of Substituents into the 3-Position of 5-Unsubstituted 4-O-Alkyl Tetronates

Paintner¹,

Allmendinger²,

Bauschke³

2005

Synlett

Self Cite

View full text Add to dashboard Cite

show abstract

“…= 95:5) by ruthenium-catalyzed cis-dihydroxylation 5 [RuCl 3 ×(H 2 O) 3 (0.07 equiv), NaIO 4 (1.5 equiv), MeCN, EtOAc, H 2 O, 0 °C, 3 min] of the known acyl tetronate 7. 6 The relative stereochemistry between C-3, C-4 and C-5 in 8 was determined on the basis of 1 H-1 H J-coupling values and NOE studies. To effect the desired cyclization we em- In light of these failures we examined the cyclization of the model system 7 to get a more basic insight into the key ring closure step (Scheme 3).…”

mentioning

confidence: 99%

“…Thus catalytic hydrogenation of 7 and subsequent treatment of the respective 3-acyl tetronate with catalytic amounts of concentrated sulfuric acid resulted in the exclusive formation of the tetrahydrofuranylidene tetrahydrofuran-2,4-diones 14 (90% yield, ~ 1:1 mixture of E-Z isomers). An alternative approach to the desired ring skeleton, which avoids the generation of an allyl cation intermediate, was envisioned to arise from tetronate building blocks such as 17 6 by a fluoride ion induced desilylation-cyclization sequence (Scheme 5). Indeed, treatment of 17 with tetrabutylammonium fluoride [TBAF×3H 2 O (1.0 equiv), THF, r.t.] afforded the tricyclic intermediate 18.…”

mentioning

confidence: 99%

Synthetic Studies Toward Tetrodecamycin: An Efficient Approach to the Core Structure of the Antibiotic

Paintner¹,

Allmendinger²,

Bauschke³

et al. 2002

Synlett

Self Cite

View full text Add to dashboard Cite

S y n t h e t i c S t u d i e s t o w a r d T e t r o d e c a m y c i nAbstract: An efficient synthetic pathway to the core structure 5 of the polyketide antibiotic tetrodecamycin (1a) has been developed. Our approach features the acid-catalyzed cyclization of a tert-butyldimethylsilyl protected methyl a-(g-hydroxyacyl) tetronate, leading to the novel tricyclic ring skeleton exhibited by 5. An insight into the mechanism of this key ring closure step has been gained. Furthermore an alternative pathway to this ring skeleton, based on a fluoride ion induced desilylation-cyclization sequence, has been disclosed. Tetrodecamycin (1a) and its dihydro derivative 1b ( Figure 1) are novel polyketide antibiotics isolated from Streptomyces nashvillensis in 1994 by Takeuchi and coworkers. 1 The former was shown to exhibit promising activity against Gram-positive bacteria including Bacillus anthracis as well as methicillin resistant Staphylococcus aureus (MRSA). The latter, however, is virtually inactive revealing the crucial role of the exo-methylene moiety in 1a for biological activity. Their unique tetracyclic ring skeleton comprises a a-(g-hydroxyacyl) tetronic acid derived 3,4-dihydro-2H,8H-furo[3,4-b]oxepine-5,6-dione (2) partial structure. This structural feature is highly remarkable, in so far as all other anhydro a-(g-hydroxyacyl)tetronic acids known solely exist in the isomeric tetrahydrofuranylidene tetrahydrofuran-2,4-dione form [e.g. dehydrocarolic acid (3)]. 2Recently we described an approach to a tricyclic substructure 4 of tetrodecamycin (1a), containing the crucial seven-membered ring (Scheme 1). 3,4 In the course of further investigations, however, it became clear, that final osmium tetroxide promoted cis-dihydroxylation of 4 to obtain the model system 5 is unfeasible, due to an exclusive attack of the reagent on the exo-methylene moiety. Thus reaction of 4 with osmium tetroxide (0.02 equiv) and N-methylmorpholine N-oxide (1.2 equiv) as co-oxidant (t-BuOH, acetone, H 2 O, r.t.) gave diol 6 (68% yield).Herein we report further model studies toward the total synthesis of tetrodecamycin, culminating in an efficient synthetic pathway to the core structure 5 of the antibiotic. According to the results mentioned above it was obvious to introduce the syn diol group at an early stage of the synthesis prior to the generation of the exo-methylene moiety. Hence our initial efforts to obtain 5 involved the preparation and acid-catalyzed cyclization of acyl tetronate 8 (Scheme 2).Cyclization precursor 8 was readily obtained in 68% yield (d.s. = 95:5) by ruthenium-catalyzed cis-dihydroxylation 5 [RuCl 3 ×(H 2 O) 3 (0.07 equiv), NaIO 4 (1.5 equiv), MeCN, EtOAc, H 2 O, 0 °C, 3 min] of the known acyl tetronate 7. 6 The relative stereochemistry between C-3, C-4 and C-5 in 8 was determined on the basis of 1 H-1 H J-coupling values and NOE studies. To effect the desired cyclization we emScheme 1 (a) OsO 4 (0.02 equiv), NMO (1.2 equiv), t-BuOH, acetone, H 2 O, r.t. (68%) Figure 1Downloaded by: University of Florida. Copyrighted ...

show abstract

Di-n-butylboryl Trifluoromethanesulfonate

Garvey

Flamme²,

Methot³

2004

Encyclopedia of Reagents for Organic Synthesis

View full text Add to dashboard Cite

Highly Regioselective 3-Hydroxyalkylations of Boron 4-Methoxy-2-furanolates: A New Entry to 5-Unsubstituted and 5-Monosubstituted 3-Acyl-4-O-Methyl Tetronates

Cited by 20 publications

References 5 publications

A General Method for the Highly Regioselective Introduction of Substituents into the 3-Position of 5-Unsubstituted 4-O-Alkyl Tetronates

A General Method for the Highly Regioselective Introduction of Substituents into the 3-Position of 5-Unsubstituted 4-O-Alkyl Tetronates

Synthetic Studies Toward Tetrodecamycin: An Efficient Approach to the Core Structure of the Antibiotic

Di-n-butylboryl Trifluoromethanesulfonate

Contact Info

Product

Resources

About