71276-94-3Relevant academic research and scientific papers
CONTROLLED FORMATION OF DIPYRANOSIDE DERIVATIVES THROUGH C6 AND 04. PYRANOSIDIC HOMOLOGATION. VII
Molino, Bruce Francis,Fraser-Reid, Bert
, p. 2834 - 2842 (2007/10/02)
A procedure has been developed for pyranosidic homologation of methyl α-D-glucopyranoside via C4 and C6.Reaction of the aldehydo group of compound 2 with the Wittig-Bestmann reagent, Ph3P=CHCH(OEt)2, gave an E/Z mixture of acetals, 4, which cyclizes under
Tripyranoside Precursors for Ansamycins. Pyranosidic Homologation. 6.
Fraser-Reid, Bert,Molino, Bruce F.,Magdzinski, Leon,Mootoo, David R.
, p. 4505 - 4511 (2007/10/02)
The primary and secondary alcohols of the dipyranoses 6 and 9a are used as implements for elaborating the upper pyranoside rings of the tripyranoses 27 and 28, respectively.Compounds 27 contains seven of the eight chiral centers of rifamycin S, while 28 fixes seven of the nine chiral centers of streptovaricin A.For the synthetic procedures, the primary alcohol is oxidized to an aldehyde, which is subjected to olefination with a phosphorane of the type PH3P=CHCH(OR)2.Treatment with pyridinium p-toluenesulfonate, specifically, in the presence of an alcohol causes cycliz ation with secondary the alcohol, resulting in a hexenepyranoside, which is glycositated in situ by the alcohol.The resulting hexenepyranoside is then epoxidized, and for this process, a new procedure was developed that involves hydroxylation with osmium tetroxide and treatment of the cis diol so formed with phosgene iminium chloride (Viehe's salt> to give a chloro carbamate, which then reacts with methoxide to give the desired epoxide.Opening of the ring with dimethylmagnesium then completes the requirements for the upper ring.
Cumulated Ylides, XII. A Stereoselective Synthetic Method for (Z)-α,β-Unsaturated Aldehydes
Bestmann, Hans Juergen,Roth, Kurt,Ettlinger, Manfred
, p. 161 - 171 (2007/10/02)
(2-Ethoxyvinyl)triphenylphosphonium bromide (5) is converted with sodium amide into the corresponding phosphaallenylide 6 which adds ethanol forming the ylide 7. 7 is also obtained by the reaction of 5 with sodium ethanolate.The Wittig reaction of 7 with aldehydes 2 proceeds with high (Z)-stereoselectivity to give (Z)-α,β-unsaturated acetals 8 which are cleaved under well defined conditions with p-toluenesulfonic acid or with wet silica gel to (Z)-α,β-unsaturated aldehydes 9.
A Novel Stereoselective Synthesis of the "Pear Ester" Ethyl (2E,4Z)-2,4-Decadienoate
Bestmann, Hans Juergen,Suess, Joachim
, p. 363 - 365 (2007/10/02)
The title compound 8 is prepared by two stereoselective Wittig olefinations.
