Synthesis 2012; 44(15): 2365-2373
DOI: 10.1055/s-0031-1289809
paper
© Georg Thieme Verlag Stuttgart · New York

An Efficient Method for the Refinement of 1,3-Methyleneglycerol via Bridged Acetal Exchange and the Synthesis of a Symmetrically Branched Glycerol Trimer

Hatsuhiko Hattori
Department of Pharmaceutical Chemistry, Institute of Health Biosciences, Graduate School of The University of Tokushima, 1-78-1, Sho-machi, Tokushima 770-8505, Japan, Fax: +81(88)6337284   eMail: nem@ph.tokushima-u.ac.jp
,
Tsuyoshi Matsushita
Department of Pharmaceutical Chemistry, Institute of Health Biosciences, Graduate School of The University of Tokushima, 1-78-1, Sho-machi, Tokushima 770-8505, Japan, Fax: +81(88)6337284   eMail: nem@ph.tokushima-u.ac.jp
,
Kohsuke Yoshitomi
Department of Pharmaceutical Chemistry, Institute of Health Biosciences, Graduate School of The University of Tokushima, 1-78-1, Sho-machi, Tokushima 770-8505, Japan, Fax: +81(88)6337284   eMail: nem@ph.tokushima-u.ac.jp
,
Ayato Katagiri
Department of Pharmaceutical Chemistry, Institute of Health Biosciences, Graduate School of The University of Tokushima, 1-78-1, Sho-machi, Tokushima 770-8505, Japan, Fax: +81(88)6337284   eMail: nem@ph.tokushima-u.ac.jp
,
Hisao Nemoto*
Department of Pharmaceutical Chemistry, Institute of Health Biosciences, Graduate School of The University of Tokushima, 1-78-1, Sho-machi, Tokushima 770-8505, Japan, Fax: +81(88)6337284   eMail: nem@ph.tokushima-u.ac.jp
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Publikationsverlauf

Received: 27. März 2012

Accepted after revision: 14. Mai 2012

Publikationsdatum:
28. Juni 2012 (online)


Abstract

Acid-catalyzed equilibrium of a mixture of 1,2- and 1,3-methyleneglycerol in 1,4-dioxane affords predominantly the 1,3-isomer via bridged acetal exchange. The minor 1,2-isomer is removed via sequential pivaloylation and tritylation to afford the desired 1,3-isomer in >99.5% purity. A symmetrically branched triglycerol is efficiently synthesized starting from the purified 1,3-isomer.

Supporting Information

 
  • References

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  • 18 TrCl: The reaction of cGF with trityl chloride was abandoned because deprotecting conditions to recycle the reagent must be carefully controlled for tritylated 7 and 8 in the presence of acetal protecting groups. Alternatively, exhaustive hydrolysis to afford glycerol, formaldehyde and trityl alcohol must be performed
  • 20 The hypothesis shown in Figure 3 becomes more credible as a consequence of the results reported herein, because the results of entries 8, 12 and 13 in Table 1 indicate objectively the balanced point of thermodynamic equilibrium. The conditions for the industrial preparation of cGF must undoubtedly be different from our reported conditions, although the industrial preparation was not described in detail
  • 21 Undesired compound 8 was obtained as the major isomer when halogenated solvents such as CH2Cl2 or DCE were chosen for the acid-catalyzed re-bridge reaction of cGF. Additionally, wet ethereal solvents and/or wet glycerol afforded less 7 and more 8 than the result obtained in entry 8. Therefore, the thermodynamic ratio (7:8 = 77:23) was reached as long as anhydrous conditions were carefully maintained
  • 22 Treatment of compound 7 (of 97% purity) with TrCl afforded 7 in much higher purity than similar treatment with PvCl. Although we pointed out that tritylation of methyleneglycerol was problematic if recycling results of 25–44% of 8 were considered,18 using TrCl to remove the very small amount of 8 (Scheme 9) was acceptable for our purposes
  • 23 Extraction is often more economical and sustainable than distillation since time and energy (electricity for running the vacuum pump and heating equipment) can be saved. Therefore, the separation procedure by extraction with hexane was also examined for removing pivaloylated compounds from 7 and 8, which proved to be as successful as the tritylation procedure