Synthesis of the C(1)C(16) fragment of bryostatins

Allylsilanes in Organic Synthesis − Recent Developments

“…Scheme 51 The total synthesis of (ϩ)-189 has been achieved by a straightforward four-step procedure, giving an overall yield of 68% starting from (ϩ)-186, and a similar H-ene reaction with an ynone has been used for the elaboration of the C-1ϪC-16 fragment of brystatins. [100] The H-ene reaction can also be performed between an allylsilane and a carbonyl derivative.…”

Total Synthesis of Spirotenuipesines A and B

“…47 ) were unsuccessful, presumably due to low reactivity or to 1,2-elimination of the cuprate, which would lead to unproductive formation of allene. 42,43 An alternate cuprate reagent, derived from 1-bromo-1-trimethylsilylmethylethene,(44) was chosen to avoid the problem of 1,2-elimination. The expectation was that the TMS group could be subsequently transformed into the requisite hydroxyl group.…”

Approaches to the total synthesis of biologically active natural products: studies directed towards bryostatins

“…3) (97) Phytochem Rev (2010) 9:501-513 511 1998), the zinc diiodide promoted ''ene'' reaction between an allylsilane and an alkynone which retains stereoselectively the trimethylsilyl group ( Fig. 4) (O'Brien et al 2002), the palladium(0) catalysed coupling of a tin enolate formed in situ with a vinylic bromide for stereoselective bc-alkenone synthesis ( Fig. 7; Almendros et al 2000), the 2-(1-benzothiazol-2-yl-2-methylprop-2-yl)-1,3-dithiane (70) as a difunctionalised reagent for (E)-selective alkene synthesis (Allen et al 2008), and the bismuth(0) promoted reaction of an allylic bromide and an aldehyde in the presence of other reactive functionalities such as an acrylate or a benzothiazolyl sulfone (Fig.…”

“…3). This cyclisation gave an 85:15 mixture of epimers at C(2) which were separated as their acetates (14), and formed the basis of a subsequent synthesis of the 1,16-fragment of the bryostatins (O'Brien et al 2002). The zinc diiodide mediated ''ene'' reaction between the allylsilane (15) and the conjugated alkynyl ketone (16) proceeded with retention of the trimethylsilyl group and gave the (E)-vinylsilane (17) stereoselectively.…”