Stilbene trimers

E stands for trans, Z stands for cis Fig. (32). Structures of stilbene trimers (continued)... 

Four new glycosides of stilbene trimer, termed foeniculosides I, II, III and IV (664-667), were isolated from the fruit of Foeniculum vulgare Miller along with miyabenol C and cA-miyabenol C (663) [302]. The structures of trimers are illustrated in Fig. (31)-Fig. (35). 

Huang KS, Li RL, Wang YH, Lin M (2001) Three new stilbene trimers from the lianas of Gnetum hainanense. Planta Med 67 61-64... 

The same phenomenon was found in the polymerization (to dimers and trimers) of trans-stilbene by TiCl4-CCl3COOH in benzene [8]. In this case chain initiation is presumably by protons, and there appears to be no kinetic termination at all. 

Acidolysis of spruce and/or birch lignins results in the formation of the dimeric products 8-21 (Fig- 6.1.5) (Lundquist 1976). Products 8-16 originate from structural elements of the / -1 type (22). Acidolysis of trimeric sequences of lignin units of type 23 gives rise to phenylcoumarone 17 and stilbene 18- Structures of fl-[i type are the sources of compounds 19-21. 

Numerous stilbenes such as e-viniferin (Landrault et al. 2002) and 5-viniferin, two resveratrol dehydrodimers (Vitrac et al. 2005), the resveratrol dimer pallidol (Vitrac et al. 2001), a-viniferin, a trimer of resveratrol (Pryce and Langcake 1977)... 

Thiobenzaldehyde trimer, (CgHjCHS), is decomposed at 230° by freshly reduced copper powder to give stilbene, CgHjCH—CHCgH, (45%). Several benzologs and alkoxyl derivatives of stilbene have been prepared by this method in low yields. The trimers of the thioaldehydes are readily prepared from their oxy analogs, hydrochloric acid, and hydrogen sulfide. 

Resveratrol dehydrodimers have also been enzymically transformed from resveratrol (1) accompanied by HRP/H2O2 [381] and other peroxidases, pallidol, resveratrol rram-dehydrodimer (553), and leachianol F (515) but not e-viniferin (445) [251,381]. The trimeric stilbene (+)-davidiol A (652) was successfully transformed from (+)-e-viniferin (445) and resveratrol by HRP [301]. Laccases from Myceliophtora thermophyla and Trametes pubescens could be used for the selective oxidation of resveratrol (1) on a preparative scale to give compound 553 [382]. Similarly, incubation of pterostilbene (7) by laccase of B. cinerea led to pterostilbene dehydrodimers (558, 559) [252]. Candida antarctica lipase could regioselectively catalyze acetylation and alcoholysis of resveratrol (1) and analogs [383]. 

Polydimethylsiloxane (PDMS) was synthesized from the cyclic trimer hexa-methyltrisiloxane D3 in hexane using anionic ring-opening polymerization and dilithium stilbene as initiator (7). This material was terminated by chlorovinyldi-methylsilane at a molecular weight Mw of 60,000. It was then precipitated from... 

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