Sugar Allyltin Compounds: Preparation and Application in Organic Synthesis

Abstract

General methodology for the preparation of allyltin derivatives is reported, with special attention paid to sugar allyltins. Typical procedures affording such organometallics involve the conversion of partially protected hexoses or pentoses (Sug–CH2OH) into homologated allylic alcohols (Sug–CH=CH–CH2OH), which are further transformed into the primary or secondary sugar allyltin derivatives of the general formula Sug–CH=CH–CH2SnR3, (E)/(Z) ratio ≈ 5:1, or Sug–CH*(SnR3)–CH=CH2 (single isomer with the (S)‐configuration at the newly created chiral center*). Controlled Lewis acid‐induced fragmentation of these hexose‐derived organometallics provides highly oxygenated dienoaldehydes with the (E) geometry across the internal double bond: CH2=CH–CH=CH–[CH(OR)]3–CHO. The (Z)‐dienoaldehydes are also available by thermal fragmentation of the secondary sugar allyltins. Both these synthons ((E) and (Z)) can be further converted into highly functionalized derivatives of bicyclo[4.3.0]nonene and bicyclo[4.4.0]decene. Stereochemical aspects of reactions between sugar allyltins and sugar aldehydes (in the presence of Lewis acids or under high pressure) are also discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Chemical Synthesis of a Glycolipid Library by a Solid‐Phase Strategy Allows Elucidation of the Structural Specificity of Immunostimulation by Rhamnolipids

“…At high stannane concentrations (Scheme , a), hydrogen transfer from the tributyltin hydride takes place more rapidly than radical cyclization, to give the open‐chain alkenylstannane31 21a (see also 20a → 13a → 21a in Scheme ). At low stannane concentrations (syringe pump addition), though, the vinyl radical 13 (R = SnBu 3 ) is able to undergo the – slow – 6‐ endo ‐ trig cyclization more rapidly than hydrogen transfer, thus leading to the tricyclic radical 24 .…”

The Crotylation Way to Glycosphingolipids: Synthesis of Analogues of KRN7000

“…16,17 Unlike more conventional approaches to glycomimetics, this strategy does not focus on the creation of the glycoside (or pseudoglycoside) bond, but on other linkages, thereby avoiding complications with challenging glycoside isosteres, while opening entry to new glycomimetic space.…”

“…18,19 Thus 7 , 10 and 13 were prepared following the studies by Jarosz, from allylic alcohol precursors 6 , 9 and 12 respectively. 17 For 7 , 6 20 was first converted to the xanthate derivative. Thermal rearrangement of the latter and in situ treatment of the resulting secondary dithiocarbonate with Bu 3 SnH in the presence of AIBN, gave crotyltin 7 with an E : Z ratio of 3:2, in 57% overall yield from 6 .…”

“…While crotylations with sugar-derived crotylstannanes and aldehydes have been documented, the potential of this reaction for glycomimetic synthesis has not been fully tapped. , Unlike more conventional approaches to glycomimetics, this strategy does not focus on the creation of the glycoside (or pseudoglycoside) bond, but on other linkages, thereby avoiding complications with challenging glycoside isosteres, while opening entry to new glycomimetic space.…”

“…For the preliminary test of this methodology, tin-based reagents were chosen because of their ease of preparation and greater stability compared to other classes of crotylating agents (Scheme ). , Thus, 7 , 10 , and 13 were prepared following the studies by Jarosz, from allylic alcohol precursors 6 , 9 , and 12 respectively . For 7 , 6 was first converted to the xanthate derivative.…”