Stereoselective Synthesis of the A-Ring of Armatol A from a Bromo-substituted Chiral Building Block Based on Ireland-Claisen Rearrangement and Ring-Closing Olefin Metathesis

Heterocycles ◽  
2015 ◽  
Vol 91 (1) ◽  
pp. 76 ◽  
Author(s):  
Kenshu Fujiwara ◽  
Yuta Hirose ◽  
Takafumi Saito ◽  
Ryo Katoono ◽  
Takanori Suzuki
Keyword(s):  
Building Block ◽  
Olefin Metathesis ◽  
Claisen Rearrangement ◽  
Stereoselective Synthesis ◽  
Chiral Building Block ◽  
Block Based

scholarly journals Two Complementary Synthetic Approaches to the Enantiomeric Forms of the Chiral Building Block (2,6,6-Trimethyltetrahydro-2H-pyran-2-yl)methanol: Application to the Stereospecific Preparation of the Natural Flavor Linaloyl Oxide

Catalysts ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 362 ◽  
Author(s):  
Stefano Serra ◽  
Davide De Simeis
Keyword(s):  
Fractional Crystallization ◽  
Building Block ◽  
Large Scale ◽  
Stereoselective Synthesis ◽  
Optical Purity ◽  
Building Blocks ◽  
Synthetic Approach ◽  
Racemic Form ◽  
Chiral Building Block ◽  
Synthetic Approaches

The enantiomeric forms of the alcohol (2,6,6-trimethyltetrahydro-2H-pyran-2-yl)methanol are potential chiral building blocks for the stereoselective synthesis of different natural terpenes. Here, we describe their preparation by means of two different synthetic approaches. The first is based on the stereospecific (+)-10-camphorsulfonic acid (CSA)-catalyzed cyclization of (R)- and (S)-2-methyl-5-(2-methyloxiran-2-yl)pentan-2-ol, which were in turn synthesized from (R)- and (S)-linalool, respectively. The latter monoterpenes are easily available from the chiral pool, with different optical purity. As our synthesis makes use of the intermediate 2,6-dimethyloct-7-ene-2,6-diol, whose enantiopurity can be improved through fractional crystallization, we obtained (2,6,6-trimethyltetrahydro-2H-pyran-2-yl)methanol enantiomers in an almost enantiopure form. The second synthetic approach is based on the lipase-mediated resolution of the aforementioned tetrahydropyranyl alcohol, which was prepared in racemic form starting from the industrial intermediate, dehydrolinalool. In this work, we report a large-scale resolution procedure that exploits the opposite enantioselectivity of Novozym® 435 lipase and lipase AK in the acetylation reaction of (2,6,6-trimethyltetrahydro-2H-pyran-2-yl)methanol. The two enantiomeric forms of the latter alcohol were employed for the first stereoselective synthesis of both enantiomers of the flavor, linaloyl oxide (2,2,6-trimethyl-6-vinyltetrahydro-2H-pyran).

scholarly journals Use of (S)-trans-γ-Monocyclofarnesol as a Useful Chiral Building Block for the Stereoselective Synthesis of Diterpenic Natural Products

2014 ◽  
Vol 9 (3) ◽  
pp. 1934578X1400900 ◽  
Author(s):  
Stefano Serra ◽  
Alessandra A. Cominetti ◽  
Veronica Lissoni
Keyword(s):  
Natural Products ◽  
Building Block ◽  
Stereoselective Synthesis ◽  
Allyl Acetate ◽  
Chiral Building Block ◽  
Sulfone Derivative ◽  
Key Steps ◽  
First Time ◽  
Unambiguous Assignment ◽  
Comprehensive Study

A comprehensive study of the exploitation of ( S)- trans-γ-monocyclofarnesol as a useful chiral building block for the stereoselective synthesis of natural diterpene derivatives is here described. The farnesol derivative (+)-1 was used as starting material in the preparation of the diterpenes ( S)-dehydroambliol-A and ( S)-trixagol, as well as for the syntheses of the dinorditerpene ( S)-dinortrixagone and of the guanidine-interrupted terpenoid ( S)-dotofide. Key steps of the presented syntheses were the cross-coupling between an allyl acetate and a Grignard reagent, the Wittig reaction, the selective preparation of a diacylguanidine derivative and the alkylation of a sulfone derivative, followed by the reductive removal of the same functional group. It is worth noting that the natural products (+)-8, (+)-12 and (+)-15 were prepared stereoselectively for the first time, thus allowing the unambiguous assignment of their absolute configuration.

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