A Convenient One-flask Synthesis of α-Methylenealdehydes from Primary Alcohols

Abstract

A convenient one-flask synthesis of α-methylenealdehydes from primary alcohols has been established.

Total Syntheses of (+)‐Polygalolide A and (+)‐Polygalolide B: Elucidation of the Absolute Stereochemistry and Biogenetic Implications

“…Catalytic hydrogenation of the C2C10 double bond in 12 using 10 % Pd/C was followed by desilylation with AcOH‐buffered Bu 4 NF to give alcohol 14 in 91 % yield in two steps. At this juncture, the C2C3 double bond, which would serve as a dipolarophile in the key cycloaddition reaction, was installed by employing a slight modification of the protocol reported by Ogasawara and co‐workers;15 Eschenmoser’s salt and 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU)16 were added to the reaction mixture, wherein alcohol 14 underwent a Swern oxidation 17. The resultant enal 15 was further oxidized with NaClO 2 and treated with MeI under basic conditions to provide methyl ester 16 in 79 % yield in two steps.…”

Total Synthesis of Hemibrevetoxin Β via the Allylic Tin Methodology

“…7 Finally, the silyl protecting groups were removed by using S1F4 to give hemibrevetoxin Β (1) in 68% yield. 7 Finally, the silyl protecting groups were removed by using S1F4 to give hemibrevetoxin Β (1) in 68% yield.…”

Taxol: Synthesis, Bioactive Conformations, and Structure-Activity Relationships in Its Analogs

“…Ring D was built up in a way similar to the Holton synthesis, by oxidation of the corresponding double bond to diol; however, the hydroxy group on C 5 was preliminarily replaced by bromine (compound 20). Intramolecular S N 2 substitution of the bromine atom gave compound 21 possessing an oxetane fragment [14,15,18,[20][21][22][23][24][25][26]. Acylation of the hydroxy group on C 4 and removal of protecting groups afforded compound 22, and the taxol side chain was attached to 22 as in the Holton synthesis [13][14][15].…”

“…Mukaiyama also used the linear strategy (Scheme 3); however, completely functionalized ring B was built up initially from simple starting materials [27][28][29][30][31]. In the first stage, L-serine (23) was extended to five- (24) and seven-membered carbon chain (25) by condensa-tion of intermediate aldehydes with various reactants. After a series of modifications of functional groups and bromination, β-hydroxy ester 25 was converted into keto aldehyde 26, and cyclization of the latter by the action of SmI 2 gave functionalized ring B (structure 27).…”