Optically pure 1,3-diols from (2R,4R)- and (2S,4S)-1,2:4,5-diepoxypentane
摘要:
Optically pure (> 97% ee) (2R,4R)-1,2:4,5-diepoxypentane (1) and its enantiomer can be prepared in three steps from 2,4-pentanedione without the need for chromatographic purification. Diepoxide 1 is an efficient precursor to a wide variety of optically pure syn and anti 1,3-diols. Reaction with excess nucleophile gives symmetric[GRAPHICS]anti 1,3-diols in good yield. Reaction with a slight excess of alkyllithium under Ganem's conditions gives the monoepoxides 5 in good yield. Addition of a second nucleophile to monoepoxide 5 gives asymmetric anti 1,3-diols. Mitsunobu inversion of monoepoxide 5 followed by addition of a second nucleophile gives syn 1,3-diols. Optically pure syn and anti 1,3-diols are available from diepoxide 1 in one to three steps and good overall yield.
The catalyticasymmetric total synthesis of (−)‐exiguolide, a complex 20‐membered macrolide embedded with a bis(tetrahydropyran) motif, is reported. The convergent synthesisinvolves the construction of the C1–C11 tetrahydropyran segment via catalyticasymmetric allylation and Prins cyclization, and the formation of the C12–C21 phosphonate segment via catalyticasymmetric cyclocondensation reaction
Phorboxazole Synthetic Studies. 1. Construction of a C(3−19) Subtarget Exploiting an Extension of the Petasis−Ferrier Rearrangement
作者:Amos B. Smith、Patrick R. Verhoest、Kevin P. Minbiole、John J. Lim
DOI:10.1021/ol990830l
日期:1999.9.1
text] In this, the first of two letters, we outline our overall strategy for the totalsynthesis of phorboxazoles A (1) and B (2), rare oxazole-containing macrolides possessing extraordinary antimitotic activity, and describe the assembly of a C(3-19) subtarget (-)-5 for the totalsynthesis of phorboxazole A. The synthesis of (-)-5 was achieved in 15 linear steps (12% overall yield), exploiting a modification
Concise Synthesis of the Bryostatin A-Ring via Consecutive C−C Bond Forming Transfer Hydrogenations
作者:Yu Lu、Michael J. Krische
DOI:10.1021/ol901096d
日期:2009.7.16
Under the conditions of C−Cbondformingtransferhydrogenation, 1,3-propanediol 1 engages in double asymmetric carbonyl allylation to furnish the C2-symmetric diol 2. Double ozonolysis of 2 followed by TBS protection delivers aldehyde 3, which is subject to catalyst directed carbonyl reverse prenylation viatransferhydrogenation to deliver neopentyl alcohol 4 and, ultimately, the bryostatin A-ring
在C-C键形成转移氢化的条件下,1,3-丙二醇1参与双不对称羰基烯丙基化反应得到C 2对称二醇2。2 的双臭氧分解,然后是 TBS 保护提供醛3,醛3受到催化剂引导的羰基反向异戊二烯化,通过转移氢化提供新戊醇4,并最终提供苔藓抑素 A 环7。通过使用两个连续的 C-C 键形成转移氢化,埃文斯的苔藓抑素 A 环7的制备方法不到先前报道的一半。
Catalysis-Based Total Synthesis of Putative Mandelalide A
作者:Jens Willwacher、Alois Fürstner
DOI:10.1002/anie.201400605
日期:2014.4.14
A concise synthesis of the putative structure assigned to the highly cytotoxic marine macrolide mandelalide A (1) is disclosed. Specifically, an iridium‐catalyzed two‐directional Krische allylation and a cobalt‐catalyzed carbonylative epoxideopening served as convenient entry points for the preparation of the major buildingblocks. The final stages feature the first implementation of terminal‐acetylene
product total synthesis, which is remarkable in that this class of substrates had been beyond the reach of alkyne metathesis for decades. Synthetic 1, however, proved not to be identical with the natural product. In an attempt to clarify this issue, NMR spectra were simulated for 20 conceivable diastereomers by using DFT followed by DP4 analysis; however, this did not provide a reliable assignment either