
tipson-kohan prathikaranam

washington dii. yile naashanal beuro oof staanderdukalil stuvartt tipson alex kohan aadyamaayi kandethiya oru neyim prathikaranamaanu tipson-kohen prathikaranam.sii. oru panchasaara thanmaathrayile rund ayal sulphonyloxy grouppukale sink podi (zn), soodiyam iodide (ni) enniva upayogichu "n", "n"-dimethylformamide (dmf) polulla reflexing laayakathil samskarichu aparyapthamaaya carbohydrate nalkumbozhaanu tipson-kohen prathikaranam sambhavikkunnath.
pashchaathalam.
vividha prathikaranangalil upayogikkaan kazhiyunna vaividhyamaarnna nirmmaana blokkukalayathinaal aparyapthamaaya carbohydrateukal aavasyamaanu. udaaharanathinu, avaa prakrithi uthppannangalude samanvayathil idanilakkaaraayo dials-alder prathikaranatthil dynophylukalaayo oligosaakraraidukalude samanvayathil mungaamikalaayo upayogikkaam. uyarnnathum mithamayathumaaya vilavil alkeen uthppaadippikkunnathin tipson-kohen prathikaranam oru "siin" allengil "aanti" elemination samvidaanathiloode kadannupokunnu. prathikaranam ayal substituntukale aasrayichirikkunnu. glucopyranosideukalkkum maannooyraanosaidukalkkumal oru samvidaanam chuvade kaanichirikkunnu.
skeem 1: glucopyranosideukal upayogichaanu "siin" elemination sambhavikkunnath. galactopyranosideukal samanamaaya oru siin samvidaanam pinthudarunnu. athesamayam, mannopyranocydukalilaanu "aanti" elemination sambhavikkunnath. r oru methanesulphonyl ch2o2s (ems) allengil oru toluesulphonyl ch3c6h4o2s (ts) aakam.
prathikarana samvidaanam.
skeem 3: aadya sthaanachalanathe, nirakk nirnnayikkunna ghattatheyum ettavum mandagathiyilulla ghattatheyum, prarambha metteeriyal iodo-intermediattilekku parivartthanam cheiyunna ghattatheyum eee skeem chithreekarikkunnu. intermediat athivegam aparyapthamaaya panjasaarayaayi parivartthanam cheyyappedunnathinaal athu kandethanavilla. naitrajan-intermediattukal verthiricheduthathinaal sii-3-ll iodide pakaram assid upayogichulla pareekshanangal sthireekarikkappetta akramanam sambhavikkunnu. ettavum reactive muthal ettavum kuranja reactive vareyulla reactivityude kramam ithaanu β-glucopyranosideukal> β-mannopyranosideukal> α-glucopyranosideukal> α-mannopyranosideukal.
prarambha meteeriyalil sii-3 sulphonyloxy grouppumaayi thaarathamyappeduthumbol ayal axial substituvent (sulphonyloxy) ullathinaal β-mannopyraanosaidukalude prathikaranam kuranja vilavu nalkukayum β-glucopyranosideukalekal kooduthal prathikarana samayam aavasyappedukayum cheiyunnu. axial substituvent parivartthana avasthayile sterik edapedalukal vardhippikkukayum rund sulphonyloxy grouppukalude prathikoola grahanathinu kaaranamaakukayum cheiyunnu. α-glucopyranosideukalkku prarambha meteeriyalil c-3 sulphonyloxy (anomeric ooku 3 group) thaarathamyappeduthumbol β-trans-axial pakarakkaaran undu. β-"trans"-axial pakarakkaaran rund grouppukal thammilulla prathikoolamaaya sterik prathipravartthanathinu kaaranamaakunnathiloode parivartthana avasthaye swaadheenikkunnu. α-mannopairanosaidukalude kaaryatthil, ayal axial substituvent (2-sulphonyloxy group), β-"trans"-axial substituvent (anomeric ooku 3 group) enniva undu, athinaal prathikarana samayam ganyamaayi vardhippikkukayum vilavu kuraykkukayum cheiyunnu.
prathikarana saahacharyangal.
pattika 1: prathipravartthana samayavum vilavum substratil vyathyaasappedunnu. padanatthil nirddeshichittulla mattethoru substratinekkaalum prathikarana samayavum vilavum valare mikachathaayathinaalaanu tipson-kohen prathikaranatthinu ettavum mikacha substrate β-glucopyranosidane kandethiyathu.
sii-4, sii-6 ennividangalil benzylidene samrakshana grouppukalum anomeric sthaanathu oom grouppukalum sii-2, sii-3 ennivayil oo. tii. ezz grouppukalum adangiyirikkunnu. prathikarana thaapanila <aii. dii. 1> ccm