Z-Stereoselective semi-reduction of alkynes: modification of the Boland protocol

Mohamed, Yasser Mahmoud A.; Hansen, Trond Vidar

doi:10.1016/j.tet.2013.03.038

Cited by 29 publications

(24 citation statements)

References 68 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Asymmetric transfer hydrogenation using Noyori's protocol gave alcohol 49 . The diyne was stereoselectively reduced to the Z , Z ‐diene 50 using Hansen's modification of the Boland protocol . Protection of the hydroxy group as its silyl ether (to give 51 ) and reduction of the ester using DIBAL‐H gave aldehyde 31 , which represents the C‐9–C‐21 subunit.…”

Section: Resultsmentioning

confidence: 99%

A Stereoselective Synthesis of the Carbon Backbone of Phoslactomycin B

Raghavan

Patel

2017

Eur J Org Chem

View full text Add to dashboard Cite

A convergent synthesis of the entire carbon framework of phoslactomycin B is disclosed. An initial route aimed to create the C‐8 tetrasubstituted stereocentre through regioselective intermolecular coupling between an internal alkyne and an allyl silyl ether, adopting Trost's protocol, followed by [2,3] sigmatropic rearrangement. But this was not successful. In a second approach, a propargylic sulfide was rearranged to give an unsaturated ketone. This was then treated with lithio acetonitrile to create the C‐8 stereocentre selectively. The C‐4 and C‐5 stereocentres were introduced by a non‐Evans syn‐aldol reaction using Crimmins's protocol. The C‐9 and C‐11 carbinol centres were created by asymmetric transfer hydrogenation. The (Z,Z)‐diene moiety was introduced by partial reduction of a diyne following Hansen's modification of the Boland reduction reaction.

show abstract

Section: Resultsmentioning

confidence: 99%

A Stereoselective Synthesis of the Carbon Backbone of Phoslactomycin B

Raghavan

Patel

2017

Eur J Org Chem

View full text Add to dashboard Cite

show abstract

“…This was in spite of the fact that the reaction was very clean on TLC and no starting alkyne could be recovered. A substantially more efficient method for triple bond semireduction consisted in the treatment of 34 with Zn/Cu/Ag composite and TMSCl, which gave the desired Z olefin 35 in 86 % yield. A very similar yield (88 %) has been previously reported by Fürstner and co‐workers for the reduction of a slightly differently protected variant of the mandelalide aglycone .…”

Section: Resultsmentioning

confidence: 99%

“…Among the various methods available fort his transformation, reactiono ft he alkyne moiety with Co 2 (CO) 8 Chem.E ur.J.2016, 22,1292 -1300 www.chemeurj.org in yields of up to, but not exceeding 46 %. This was in spite of the fact that the reaction was very clean on TLC and no starting alkyne could be recovered.Asubstantially more efficient methodf or triple bond semireduction consisted in the treatment of 34 with Zn/Cu/Ag composite and TMSCl, [45,46] which gave the desired Z olefin 35 in 86 %y ield. Av ery similary ield (88 %) has been previously reportedb yF ürstner and co-workers for the reduction of as lightly differentlyp rotected variant of the mandelalide aglycone.…”

Section: Building Block Coupling and Final Stepsmentioning

confidence: 99%

Total Synthesis and Biological Assessment of Mandelalide A

Brütsch

Bucher

Altmann

2015

Chemistry A European J

View full text Add to dashboard Cite

A new convergent total synthesis of the marine macrolide mandelalide A (1) has been developed that is based on macrocyclic ring closure by a Shiina-type macrolactonization and the construction of the requisite precursor seco acid by a highly efficient Sonogashira cross-coupling reaction between two fragments of comparable complexity. Key steps in the elaboration of the acid building block were the enantioselective, catalytic addition of a protected acetylene to crotonaldehyde and the construction of the tetrahydropyran unit that is embedded in the macrocycle by means of an acid-catalyzed Prins reaction. The synthesis of the alcohol fragment features the formation of the trisubstituted tetrahydrofuran ring through an acetal cleavage/epoxide opening cascade reaction and a rarely used radical alkynylation of a primary alkyl iodide. Intriguingly, the dihydroxylation of a terminal double bond as part of the synthesis of this building block gave the same major product for both the α- and β-AD-mix reagents, albeit with moderate or low selectivity. Synthetic mandelalide A (1) was a potent proliferation inhibitor of A549, HT460, and H1299 human lung cancer cells in vitro, but not of SK-N-SH neuroblastoma cells. However, in no case did we observe complete cell kill even at the highest compound concentration tested (5 μm).

show abstract

“…Thus, aldehyde 36 was successfully converted to polyunsaturated ynediene 42 (74 % yield). After removal of the TBS groups with TBAF, the resulting diol 43 was subjected to Zn/Cu reduction by using the modified Boland procedure, [60] affording the desired n-3 DPA-derived analogue 44 in good yield. Assignment of the stereochemistry of the double bonds has been established by NMR spectroscopic techniques, notably the constant J 15,16 = 11.3 Hz is in good agreement with the formation of a Z-olefin in conjugated E,E,Z-trienes.…”

Section: Synthesis Of a N-3 Dpa-derived Analogue (Compound 44)mentioning

confidence: 99%

A Versatile and Stereocontrolled Total Synthesis of Dihydroxylated Docosatrienes Containing a Conjugated E,E,Z‐Triene

Dayaker¹,

Balas²

2014

Chemistry A European J

View full text Add to dashboard Cite

A versatile strategy featuring a Colvin rearrangement, hydrozirconation, a Sonogashira cross-coupling reaction and a Z-selective Wittig olefination, was successfully developed for the construction of a conjugated E,E,Z-triene subunit, flanked on both sides by two Z-allylic hydroxyl groups. This chemical pattern is found in many endogenous lipid metabolites such as maresin 1 (MaR1), neuroprotectin D1 (NPD1), and its aspirin triggered-isomer AT-NPD1, which not only counter-regulate inflammation but also actively orchestrate (at nanomolar doses) the resolution and termination program of acute inflammation while promoting wound healing, return to homeostasis and neuroprotection. Unlike previous approaches, the advantages of the present strategy are obvious, as it allows us to modify the nonpolar tail, the carboxylated head or both ends of the molecule without repeating the whole synthetic sequence (about 26-34 steps according to the literature). Thus, the first total syntheses of NPD1 methyl ester epimer (which can also be considered as an enantiomer of AT-NPD1) and its n-3 docosapentaenoic acid derived analogue were achieved from a highly functionalized and late advanced pivotal intermediate. This innovative route may be easily adapted to gain access to other dihydroxylated metabolites and analogues of polyunsaturated fatty acids containing a conjugated E,E,Z-triene subunit. Different epimers/diastereoisomers may be obtained by purchasing the suitable optically pure (S)- and/or (R)-1,2,4-butanetriol(s) as a chiral pool for both stereogenic centers.

show abstract

Z-Stereoselective semi-reduction of alkynes: modification of the Boland protocol

Cited by 29 publications

References 68 publications

A Stereoselective Synthesis of the Carbon Backbone of Phoslactomycin B

A Stereoselective Synthesis of the Carbon Backbone of Phoslactomycin B

Total Synthesis and Biological Assessment of Mandelalide A

A Versatile and Stereocontrolled Total Synthesis of Dihydroxylated Docosatrienes Containing a Conjugated E,E,Z‐Triene

Contact Info

Product

Resources

About