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Volumn 75, Issue 15, 2010, Pages 5151-5163

Synthetic efforts toward the spiroketal core of spirangien a

Author keywords

[No Author keywords available]

Indexed keywords

ALDOL ADDITION; ALKYL IODIDES; CROSS-COUPLINGS; DIASTEREOSELECTIVE; FUNCTIONALIZED; GRIGNARD REAGENT; LITHIUM ENOLATES; METHYL KETONES; STEREOGENIC CENTERS; SYNTHETIC APPROACH; SYNTHETIC STUDY; TERMINAL OLEFINS;

EID: 77955137825     PISSN: 00223263     EISSN: 15206904     Source Type: Journal    
DOI: 10.1021/jo100871m     Document Type: Article
Times cited : (34)

References (50)
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    • Chem. Abstr. 1993, 119, 180598.
    • (1993) Chem. Abstr. , vol.119 , pp. 180598
  • 17
    • 77955141706 scopus 로고    scopus 로고
    • Obtained from meso -diol (2 R*,3 S*,4 S*)-3-(tert -butyldimethylsilyloxy)-2,4-dimethyl-1,5-pentanediol 32 according to reported procedures; see refs 6 and 7
    • Obtained from meso -diol (2 R*,3 S*,4 S*)-3-(tert -butyldimethylsilyloxy)-2,4-dimethyl-1,5-pentanediol 32 according to reported procedures; see refs 6 and 7.
  • 22
    • 0001513454 scopus 로고    scopus 로고
    • For application to propargylic ketones, see
    • For application to propargylic ketones, see: Parker, K. A.; Ledeboer, M. W. J. Org. Chem. 1996, 61, 3214
    • (1996) J. Org. Chem. , vol.61 , pp. 3214
    • Parker, K.A.1    Ledeboer, M.W.2
  • 23
    • 84855638301 scopus 로고    scopus 로고
    • 1H NMR analysis and/or GC/MS analysis of the crude reaction mixture
    • 1H NMR analysis and/or GC/MS analysis of the crude reaction mixture.
  • 27
    • 84855620548 scopus 로고    scopus 로고
    • 2 was used without any acid at 40 °C, no conversion of the alkyne was noticed, whereas at 70 °C, the silyl ethers were cleaved
    • 2 was used without any acid at 40 °C, no conversion of the alkyne was noticed, whereas at 70 °C, the silyl ethers were cleaved.
  • 28
    • 45249087646 scopus 로고    scopus 로고
    • Prepared according to a reported procedure by;;; Wiley: New York,; Collect
    • Prepared according to a reported procedure by Johns, B. A.; Grant, C. M.; Marshall, J. M. Organic Synthesis; Wiley: New York, 2004; Collect. Vol. X, p 170.
    • (2004) Organic Synthesis , vol.10 , pp. 170
    • Johns, B.A.1    Grant, C.M.2    Marshall, J.M.3
  • 34
    • 84855638302 scopus 로고    scopus 로고
    • 4F in MeOH
    • 4F in MeOH.
  • 35
    • 0035802349 scopus 로고    scopus 로고
    • This method was successfully used by Paterson et al. in their synthesis of spirangien A. See ref 3 and
    • This method was successfully used by Paterson et al. in their synthesis of spirangien A. See ref 3 and Paterson, I.; Florence, G. J.; Gerlach, K.; Scott, J. P.; Sereinig, N. J. Am. Chem. Soc. 2001, 123, 9535
    • (2001) J. Am. Chem. Soc. , vol.123 , pp. 9535
    • Paterson, I.1    Florence, G.J.2    Gerlach, K.3    Scott, J.P.4    Sereinig, N.5
  • 38
    • 0037077057 scopus 로고    scopus 로고
    • 1H NMR spectrum of the crude product. Assignment of each diastereomer was hypothesized by analysis of the ABX pattern of the C22 methylene unit; see:;;;;;;;;, See Supporting Information for details. The stereochemistry was also confirmed by NOESY studies on spiroketal 22, see Supporting Information for details
    • 1H NMR spectrum of the crude product. Assignment of each diastereomer was hypothesized by analysis of the ABX pattern of the C22 methylene unit; see: Roush, W. R.; Bannister, T. D.; Wendt, M. D.; VanNieuwenhze, M. S.; Gustin, D. J.; Dilley, G. J.; Lane, G. C.; Scheidt, K. A.; Smith, W. J. J. Org. Chem. 2002, 67, 4284 See Supporting Information for details. The stereochemistry was also confirmed by NOESY studies on spiroketal 22, see Supporting Information for details.
    • (2002) J. Org. Chem. , vol.67 , pp. 4284
    • Roush, W.R.1    Bannister, T.D.2    Wendt, M.D.3    Vannieuwenhze, M.S.4    Gustin, D.J.5    Dilley, G.J.6    Lane, G.C.7    Scheidt, K.A.8    Smith, W.J.9
  • 44
    • 84855632543 scopus 로고    scopus 로고
    • 2] an excess of the reagents at 50 °C was required in order to reach full conversion of 19, but a partial degradation was also observed thus explaining the moderate 50% yield
    • 2] an excess of the reagents at 50 °C was required in order to reach full conversion of 19, but a partial degradation was also observed thus explaining the moderate 50% yield.
  • 45
    • 77955151534 scopus 로고    scopus 로고
    • Hypothetical structure for 33
    • Hypothetical structure for 33
  • 46
    • 77955148715 scopus 로고    scopus 로고
    • This side reaction was not observed by Paterson et al. (3, 4) probably because acetonide protecting groups are more labile than TBS ethers, thus allowing the use of soft acidic conditions for their deprotection. Kalesse et al. (4) clearly mentioned that when TBS ethers were used instead of TES ethers the deprotection/spiroketalisation step failed
    • This side reaction was not observed by Paterson et al. (3, 4) probably because acetonide protecting groups are more labile than TBS ethers, thus allowing the use of soft acidic conditions for their deprotection. Kalesse et al. (4) clearly mentioned that when TBS ethers were used instead of TES ethers the deprotection/spiroketalisation step failed.
  • 47
    • 84855632541 scopus 로고    scopus 로고
    • The protection of the C27 hydroxyl group as a PMB ether was first envisioned in order to avoid the side reaction observed during the HF·Py mediated spiroketalization step. Unfortunately, the iron-catalyzed cross-coupling of 34 with (E)-1-methyl-1-propenylmagnesium bromide failed in the presence of the PMB ether group, and consequently, the synthesis of the aldehyde partner for the aldol coupling could not be completed
    • The protection of the C27 hydroxyl group as a PMB ether was first envisioned in order to avoid the side reaction observed during the HF·Py mediated spiroketalization step. Unfortunately, the iron-catalyzed cross-coupling of 34 with (E)-1-methyl-1-propenylmagnesium bromide failed in the presence of the PMB ether group, and consequently, the synthesis of the aldehyde partner for the aldol coupling could not be completed.
  • 50
    • 77955156786 scopus 로고    scopus 로고
    • At this stage, we had to transform the carbamate group into an iodide in order to install the C30-C31 double bond by mean of an iron-catalyzed cross-coupling. In that goal, we first envisioned a protection of the four alcohols as TES ethers, but unfortunately, a degradation of the substrate was observed in presence of TESOTf, thus unabling us to complete the synthesis of spiroketal 1
    • At this stage, we had to transform the carbamate group into an iodide in order to install the C30-C31 double bond by mean of an iron-catalyzed cross-coupling. In that goal, we first envisioned a protection of the four alcohols as TES ethers, but unfortunately, a degradation of the substrate was observed in presence of TESOTf, thus unabling us to complete the synthesis of spiroketal 1.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.