87351-45-9Relevant academic research and scientific papers
An ester enolate-Claisen rearrangement route to substituted 4-alkylideneprolines. Studies toward a definitive structural revision of lucentamycin A
Ranatunga, Sujeewa,Kim, Jinsoo S.,Pal, Ujjwal,Del Valle, Juan R.
, p. 8962 - 8976 (2011/12/03)
Substituted 4-alkylideneprolines represent a rare class of naturally occurring amino acids with promising biological activities. Lucentamycin A is a cytotoxic, marine-derived tripeptide that harbors a 4-ethylidine-3-methylproline (Emp) residue unique among known peptide natural products. In this paper, we examine the synthesis of Emp and related 4-alkylideneprolines employing a versatile ester enolate-Claisen rearrangement. The scope and selectivity of the key rearrangement reaction are described with a number of diversely substituted glycine ester substrates. Treatment of the allyl esters with excess NaHMDS at ambient temperature gives rise to highly substituted α-allylglycine products with good to excellent diastereoselectivities. Resolution of dipeptide diastereomers and cyclization to form the pyrrolidine rings provide rapid access to stereopure prolyl dipeptides. We have applied this strategy to the synthesis of four Emp-containing isomers of lucentamycin A in pursuit of a definitive stereochemical revision of the natural product. Our studies indicate that the Emp stereogenic centers are not the source of structural misassignment. The current strategy should find broad utility in the synthesis of additional natural product analogues and related 3-alkyl-4-alkylidene prolines.
Novel Functionalized Trisubstituted Allylboronates via Hosomi-Miyaura Borylation of Functionalized Allyl Acetates
Ramachandran, P. Veeraraghavan,Pratihar, Debarshi,Biswas, Debanjan,Srivastava, Amit,Reddy, M. Venkat Ram
, p. 481 - 484 (2007/10/03)
(Equation presented) A series of novel functionalized achiral and chiral allylboronates have been synthesized via the nucleophilic addition of boronates on allyl acetates derived via vinylalumination or Baylis-Hillman reaction of aldehydes. These reagents
Vinylalumination for the Synthesis of Functionalized Allyl Alcohols, Vinylepoxides, and α-Alkylidene-β-hydroxy-γ-lactones
Ramachandran, P. Veeraraghavan,Rudd, Michael T.,Burghardt, Thomas E.,Ram Reddy, M. Venkat
, p. 9310 - 9316 (2007/10/03)
A modified hydroalumination protocol for the preparation of [α-(ethoxycarbonyl)vinyl]diisobutylaluminum and its β-methyl or -phenyl analogues was developed. These vinylaluminum reagents react with aldehydes and ketones to provide the corresponding functio
An efficient approach to (E)-β-methyl Baylis-Hillman adducts via indium-mediated allylation of aldehydes in aqueous media
Cha, Joo Hwan,Pae, Ae Nim,Choi, Kyung Il Il,Cho, Yong Seo,Koh, Hun Yeong,Lee, Eun
, p. 2079 - 2081 (2007/10/03)
A new method has been developed for the synthesis of (E)-β-methyl Baylis-Hillman adducts with high E-Z (>93%) selectivity in modest to good yields. The process consists of two steps: an indium-mediated allylation reaction and a simple base-catalyzed isomerization step. Various aldehydes were allylated with allyl bromides using indium under very mild conditions in aqueous media. The allylation reactions of aromatic and aliphatic aldehydes were largely accelerated by the presence of HCl.
An improved vinylalumination procedure replacing HMPA with NMO for the hydroalumination of α-acetylenic esters and ketones
Ramachandran, P. Veeraraghavan,Reddy, M. Venkat Ram,Rudd, Michael T.
, p. 1979 - 1980 (2007/10/03)
Replacing carcinogenic HMPA with NMO, a higher yielding, enviornmentally benign procedure for the vinylalumination of carbonyl compounds with [α-(ethoxycarbonyl)vinyl]diisobutylaluminium and its β-methyl or -phenyl analogs, as well as [α-(acetyl)vinyl]dii
A new stereospecific synthesis of unusual (Z)-β-branched Baylis- Hillman adducts
Li, Guigen,Wei, Han-Xun,Willis, Steven
, p. 4607 - 4610 (2007/10/03)
A new method has been developed for the stereospecific synthesis of unusual (Z)-β-branched Baylis-Hillman adducts with high Z/E selectivity (>99 %) in modest to good yields. The process involves successful formation of anionic β-substituted [α-(alkoxycarb
Chemistry of Substituted (α-Carbethoxyvinyl)cuprates. 2. Stereospecific Olefin Synthesis
Marino, Joseph P.,Linderman, Russell J.
, p. 4621 - 4628 (2007/10/02)
The reactivity of substituted (α-carbethoxyvinyl)cuprate reagents with various electrophiles has been studied systematically.The reaction of this type of cuprate reagent with ketones and epoxides leads to high yields of isomerically pure olefinic esters, while its condensation reaction with aldehydes produced mixtures of isomers.The stereochemistry of the condensation reaction with carbonyl compounds is explained by a steric control mechanism involving an allenoate intermediate.
