Roderick W. Bates

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Name:

Organization: Nanyang Technological University , Singapore

Department: School of Physical and Mathematical Sciences

Title: (PhD)

TOPICS

Organic Chemistry

allene

Chemicals
References

Synthesis of Allahabadolactone A

Co-reporter:Kongchen Wang and Roderick W. Bates

The Journal of Organic Chemistry December 1, 2017 Volume 82(Issue 23) pp:12624-12624

Publication Date(Web):October 24, 2017

DOI:10.1021/acs.joc.7b02368

A synthesis of allahabadolactone A is described employing diastereoselective Diels–Alder and selenocyclization reactions, starting from (R)-citronellal and propylene oxide. The Diels–Alder substrate is built up in an efficient manner by rhodium-catalyzed alkyne hydroboration and palladium-catalyzed coupling reactions of E-1,2-dichloroethene. It is observed that the Diels–Alder reaction only displays high diastereoselectivity when the diene bears an additional alkene substituent but not an alkyne substituent.

Bimetallic Catalysis: Palladium/Lanthanide co-Catalyzed Allylation of Anilines

Co-reporter:Ivan Šolić;Dominik Reich;Jieyan Lim; Roderick W. Bates

Asian Journal of Organic Chemistry 2017 Volume 6(Issue 6) pp:658-661

Publication Date(Web):2017/06/01

DOI:10.1002/ajoc.201600574

AbstractThe direct palladium catalyzed N-allylation of anilines by underivatized allyl alcohols can be achieved using lanthanide co-catalysis. The reaction works equally well with different lanthanides. Surprisingly, lanthanum acetate and lanthanum chloride can give yields comparable to or better than those obtained using lanthanum triflate. Electron-rich, unhindered anilines are the best substrates, although an aminopyridine and benzimidazole are both also efficiently allylated.

Synthesis of ()-Deoxynupharidine by Allenic Hydroxylamine Cyclisation

Co-reporter: Roderick W. Bates;Dr. Chia Juan Lim;Dr. Steven J. Collier;Dr. Joly Sukumaran

Asian Journal of Organic Chemistry 2015 Volume 4( Issue 7) pp:652-658

Publication Date(Web):

DOI:10.1002/ajoc.201500094

Abstract

(−)-Deoxynupharidine has been synthesised via an intermediate that can also be used for other Nuphar alkaloids. Significant steps include the optimised enzymatic resolution of an allenic alcohol, highly diastereoselective silver-catalysed cyclisation of an allenic hydroxylamine, selective cross-metathesis, diastereoselective intramolecular reductive amination, and stereoelectronically controlled enolate alkylation.

A total synthesis of (+)-negamycin through isoxazolidine allylation

Co-reporter:Roderick W. Bates, Rab'iah Nisha Khanizeman, Hajime Hirao, Yu Shan Tay and Patcharaporn Sae-Lao

Organic & Biomolecular Chemistry 2014 vol. 12(Issue 27) pp:4879-4884

Publication Date(Web):21 May 2014

DOI:10.1039/C4OB00537F

The β-amino acid antibiotic (+)-negamycin has been synthesised in ten steps from epichlorohydrin via Sakurai allylation of an isoxazolidine intermediate. The key allylation reaction proceeded with complete trans-selectivity, which is attributed to electrostatic attraction between the chlorine atom and the iminium ion in the Sakurai intermediate.

Synthesis of the Tetrahydropyran Fragment of Bistramide D

Co-reporter: Roderick W. Bates;Lu Li;Dr. Kalpana Palani;Wanida Phetsang;Joanna Kejun Loh

Asian Journal of Organic Chemistry 2014 Volume 3( Issue 7) pp:792-796

Publication Date(Web):

DOI:10.1002/ajoc.201402052

Abstract

A synthesis of the tetrahydropyran (THP) moiety of bistramide D has been completed by using cross-metathesis and kinetically controlled intramolecular oxa-Michael addition to form the ring with excellent trans selectivity. The C9 methyl substituent was introduced by using an unsaturated sulfone building block, which can be most effectively prepared through a combination of diastereoselective allylation and alkene isomerisation. The effect of this methyl group on subsequent cross-metathesis reactions can be mitigated by careful choice of reaction conditions.

A synthesis of 5-hydroxysedamine using hydroformylation

Co-reporter:Roderick W. Bates, Nur Filza bte Mohamed Aslam, Chi H. Tang, Oliver Simon

Tetrahedron 2014 70(12) pp: 2134-2140

Publication Date(Web):

DOI:10.1016/j.tet.2014.02.001

Synthesis of azimic acid using hydroformylation

Co-reporter:Roderick W. Bates, Sivarajan Kasinathan

Tetrahedron 2013 69(14) pp: 3088-3092

Publication Date(Web):

DOI:10.1016/j.tet.2013.01.060

A synthesis of 2-epi-fagomine using gold(I)-catalysed allene cyclisation

Co-reporter:Roderick W. Bates, Pearly Shuyi Ng

Tetrahedron Letters 2011 Volume 52(Issue 23) pp:2969-2971

Publication Date(Web):8 June 2011

DOI:10.1016/j.tetlet.2011.03.130

A synthesis of 2-epi-fagomine via a highly stereoselective gold(I)-catalysed allene cyclisation is described. The stereochemical outcome of the cyclisation is opposite to that observed in previous studies. In contrast, gold(III)-catalysed cyclisation is inefficient and gives rise to double cyclisation by-products.

Development of Intravascular Contrast Agents for MRI Using Gadolinium Chelates

Co-reporter:Krisada Kittigowittana;Dr. Chang-Tong Yang;Dr. Wai Ching Cheah;Dr. Kai-Hsiang Chuang;Chew-Yuan Tuang; Young-Tae Chang;Dr. Xavier Golay; Roderick W. Bates

ChemMedChem 2011 Volume 6( Issue 5) pp:781-787

Publication Date(Web):

DOI:10.1002/cmdc.201100066

Abstract

Two MRI contrast agents (CAs) composed of Gd-DO3A conjugated to amino acid building blocks derived from glutamic acid (CA1) and lysine (CA2) have been synthesized by using novel alkyne and propionate linkers, and subsequently characterized. In vitro cell viability assays showed insignificant cytotoxicity of both CAs at low concentrations up to 0.2 mM. The longitudinal relaxivities (r₁) of CA1 and CA2 measured at 9.4 T are 6.4 and 5.4 mM⁻¹ s⁻¹ in H₂O at 25 °C, respectively. Both r₁ values are higher than those of CAs in clinical use: Gd-DTPA (Magnevist, Bayer Schering, Germany) and Gd-DOTA (Dotarem, Guerbet, France). In vivo imaging in Wistar rats demonstrated considerable signal enhancement (∼50 %) in the brain artery by CA2, but lower signal enhancement (∼30 %) by CA1. In contrast to Dotarem, which showed a similar signal enhancement as CA2, the enhancement by CA2 remained high (∼30 %), even at 52 min post-injection. This demonstrates that CA2 has a much longer blood half-life (68.1 min), which could be advantageous for angiography and tissue targeting.

A Synthesis of Pseudoconhydrine and Its Epimer via Hydroformylation and Dihydroxylation

Co-reporter:Roderick W. Bates, K. Sivarajan, and Bernd F. Straub

The Journal of Organic Chemistry 2011 Volume 76(Issue 16) pp:6844-6848

Publication Date(Web):June 13, 2011

DOI:10.1021/jo2008912

A synthesis of the alkaloid pseudoconhydrine and its epimer has been achieved using tandem hydroformylation–condensation to form the six-membered ring and stereoselective dihydroxylation to introduce oxygenation. The stereoselectivity of dihydroxylation can be explained by lipophilic and electrostatic effects, supported by DFT calculations. The alkaloids can be obtained either by regioselective dehydroxylation or by rearrangement, followed by reduction.

Synthesis of the Stenine Ring System from Pyrrole

Co-reporter:Roderick W. Bates and S. Sridhar

The Journal of Organic Chemistry 2011 Volume 76(Issue 12) pp:5026-5035

Publication Date(Web):April 29, 2011

DOI:10.1021/jo200699k

The skeleton of the stemona alkaloid, stenine, has been synthesized starting from pyrrole, employing an asymmetric organocatalyzed cyclization, Sonogashira coupling, a diastereoselective intramolecular propargylic Barbier reaction, cyclocarbonylation, and diastereoselective alkene reduction. Modulation of the electron-rich nature of the pyrrole nucleus by employing an α-trifluoroacetyl group is essential. The α-trifluoroacetyl group may be rapidly removed under carefully defined, mild conditions.

Synthesis of (−)-Sedinine by Allene Cyclization and Iminium Ion Chemistry

Co-reporter:Roderick W. Bates and Yongna Lu

Organic Letters 2010 Volume 12(Issue 17) pp:3938-3941

Publication Date(Web):August 12, 2010

DOI:10.1021/ol1016492

A synthesis of the sedum alkaloid sedinine has been achieved employing silver(I)-catalyzed allenic hydroxylamine cyclization and ring-closing metathesis to form a bicyclic N,O-acetal. Ring opening of this acetal with a silyl enol ether under Lewis acidic conditions is exclusively trans selective, leading to the natural product after reduction. On the other hand, conversion of the bicyclic N,O-acetal to a semicyclic N,O-acetal results in no stereoselectivity during such a reaction. The contrasting results can be rationalized by consideration of the conformation of the iminium ions.

Synthesis of the Northern hemisphere of the briaranes

Co-reporter:Roderick W. Bates, Attapol Pinsa, Ximin Kan

Tetrahedron 2010 66(33) pp: 6340-6348

Publication Date(Web):

DOI:10.1016/j.tet.2010.04.003

A Formal Synthesis of Swainsonine by Gold-Catalyzed Allene Cyclization

Co-reporter:Roderick W. Bates and Mark R. Dewey

Organic Letters 2009 Volume 11(Issue 16) pp:3706-3708

Publication Date(Web):July 29, 2009

DOI:10.1021/ol901094h

A formal synthesis of swainsonine has been achieved using a highly efficient and diastereoselective gold(III)-catalyzed allene cyclization.

Ring opening of cyclic N,O-acetals with allyltrimethylsilane under Lewis acidic conditions