title: Stereodivergent Synthesis and Stereochemical Reassignment of the C79-C104 Fragment of Symbiodinolide.
abstract: We have synthesized eight possible diastereoisomers 3 a-h of the C79-C97 fragment of symbiodinolide (1) in a stereodivergent manner by utilizing a dithiane addition to the aldehyde as a key step. Comparison of the13C NMR chemical shifts of the natural product 1 and the synthetic products 3 a-h indicated that the relative stereostructure of this fragment in symbiodinolide (1) is that represented in 3 a or f. We have stereodivergently synthesized eight possible diastereoisomers of the C94-C104 fragment 4 a-h, and we have compared their13C NMR chemical shifts with those of the natural product, which established the relative stereochemistry of this fragment to be that described in diastereoisomers 4 a or e. By combining the stereostructural outcomes of the C79-C97 and C94-C104 fragments, we have proposed four candidate compounds of the C79-C104 fragment 2 a-d. We also synthesized diastereoisomers 2 a and b (2 a in the preceding article; Chem. Eur. J. 2015, DOI: 10.1002/chem.201503880) by a Julia-Kocienski olefination and diastereoisomers 2 c and d by a Wittig reaction. By comparing the13C NMR chemical shifts of natural symbiodinolide (1) with those of the synthetic products 2 a-d, we have reassigned the stereostructure of the C79-C104 fragment of natural product 1 to be that depicted in diastereoisomer 2 b.
authors.affiliation: Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kita-ku, Okayama, 700-8530, Japan. takamura@cc.okayama-u.ac.jp.
authors.forename: Hiroyoshi
authors.identifier: http://orcid.org/0000-0002-8330-969X
authors.initials: H
authors.lastname: Takamura
authors.affiliation: Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kita-ku, Okayama, 700-8530, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Fujiwara
authors.affiliation: Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kita-ku, Okayama, 700-8530, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Kawakubo
authors.affiliation: Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushimanaka, Kita-ku, Okayama, 700-8530, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Kadota
authors.affiliation: Department of Chemistry, Faculty of Science, Kanagawa University, 2946 Tsuchiya, Hiratsuka, 259-1293, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Uemura
keywords: macrocycles; natural products; polyols; stereodivergent synthesis; structure elucidation