Synthetic Efforts Toward Ryanodine and Ryanodol - The Stoltz Group

Ryanodine ReactivityHO23AROHOHO124EHO1511OHBODR=H, RyanodolO1H10OHR=N, Ryanodine59C21- Cage-like shape of molecule prevents selective ester formationat C3; esterification occurs at C10.- Dehydration occurs in the presence of acid to formanhydroryanodine. This major degradation product waskey to elucidation of absolute structure.- Due to the bridgehead nature of the molecule, stereocentersat C1, C5, C11, C12, and C15 are geometrically related.- Deslongchamps uses this rationale to focus on setting theother six stereocenters en route to anhydroryanodol, thetargeted precursor to (+)-ryanodol.RyanodolH 3 O +H 2 O + HOH 2 OHOHO HOOOHOHHOHOHO HOOOHOAnhydroryanodolRelated RyanoidsHOHOHO HOOHHOHOHOOHOOOOOO20OHHNOHHNOH9,21-didehydroryanodineMajor component of ryania extracts; equipotentinsecticide as ryanodine.SpiganthineIsolated from Spigelia anthelmia; found with ryanodine.HOHOHO HOOHHO18HOHOHO HOOHHOHOHOHOOH10O3 3O3OOHCinnzeylanol Cincassiol B PerseanolNon-alkaloidal ryanoids isolated from the Cinnamonum genus; insecticidal. Isolated from Persea indica, the tree thatryanodol was first isolated.OHOH

Biosynthesis and Biological Activity21310HO2HOHO HO1310OH351514OHGeranyl Geraniol3ROOOH515 14OH- Thought to be derived from geranyl geraniol; however, "the mechanism of carbon-carbon bond formation...is not obvious... nor is that of introducing the required hydroxyl functionalities."- Effects on calcium levels were known for some time, but it wasn't until 9,21-didehydroryanodine wasisolated that the receptor could be identified (via [3H]-labeled derivative)- RyRs are a family of calicum channels that release Ca from intracellular stores; physically the largest ionchannel known, RyRs exist as a homotetramer.- Understanding of the binding site is unclear; at low [ryanodine], the receptor is at partial (50%) to fullconductance; however, at high [ryanodine], the channel is in a closed state.- The !-pyrrole ester is necessary for biological activity; ryanodol has lost all affinity for RyR. The next mostimportant feature is the shape of the ryanoid skeleton. It is believed that ryanodine binds the receptor with thehydrophobic surface, exposing the polar alcohol functionalities.- Total synthesis efforts could provide analogs not accessible through degradation, facilitating elucidation ofbinding models, biosynthesis, binding site characteristics, and provide clues about endogenous RyR ligands.2+Retrosynthesis of RyanodineOH OHHO HOHOOHHOOHOH OHHO HOHO OOHOHNRyanodineOHOH OHHO HOHOOHHORyanodolOHOHHO HOOHOO+OOH OHOOAnhydroryanodolOOCH 3(S)O

Synthesis of o-Spirolactone DienoneOH OHHO17 HOHOOHHOOHMeO1. CH 3 OCHCl 2 , TiCl 4 , CH 2 Cl 2HO2. BBr 3 , CH 2 Cl 2MeO80%HOCHO1. BrCH 2 COBr, Pyr, PhH2. Na 2 CO 3 , THFOOWolff-Kishner80%O80%CHOOONaOH, H 2 O, MeCN, NBSOOOCH 395%OOCH 3Synthesis of Vinylketone AcetalOH OHHO17 HOHOOHHOOHPt/H 2 , Et 2 O1. O 3 , EtOAc2. (CH 2 OH) 2 , p-TsOH, PhH3. MeI, K 2 CO 3 , CH 3 COCH 3O80%O70%from (+)-carvoneCH 3(+)-CarvoneCH 3MeO 2 COO1. NaOH, MeOH2. LiH, THF, CH 2 =CHLi75%OOO

Ozonolysis and Aldol Condensation –the C RingOH OH 10 OHHO HO11 6HOOHHO10O OOH O 3 , EtOAc, p-TsOH;6 11LDA, THF, -78°C;Me 2 SH O OH Et 3 B, -25°C; MeIO> 90%H OO70%OXHHOOOOMeOMeOO O1) NaBHH O OH4 , MeOHH OOTHF, 0°C, > 95%H O 10 OX2) MOMCl, NaH THFH O HO680% + 13% SMX11OOOOX = –CH(OCH 3 ) 2Ozonolysis and Aldol CondensationOH OHHO HOHOOHHOOHOHOOOHOOMeOMeHO 3 , EtOAc, p-TsOH;Me 2 S> 90%OHOOOOHXOOHHHXOOOOHOOOAldolHHXOOOHOOHHHXOOOHOOHHXOOOOOHOOUndesiredOOOO

Grob Fragmentation to a Macrolactone –Strategy for the D RingOH OH17HOHO11HOOHHO15OHHHXOOOO HO17O1115OO1) LAH, THF, 95%2) CrO 3 •2Py, CH 2 Cl 2-45 to -22 °C, 76%3) MsCl, Py, 0 °C,89%HHXOOO ROOR = MsOOOHO LiSDMSOHHXOOO ROOOOO –HHX17OOOOO1115OOHBF 4 , THF,0 °C92%(2 steps)X = –CH(OCH 3 ) 2HHXOOOOOOHD Ring Formation and FGIOH OH17HOHHO113OHOHO15OHHHX17OOOOO1115OH1) CF 3 CO 3 H, Na 2 HPO 4DCE, 4 °C2) NaOH, MeOCH 2 CH 2 OMe77% over 2 stepsHHXHOOOOOOOHOH1) pNBClPy, 0 °C2) CrO 3 •2PyCH 2 Cl 2 , 78%HHXOOpNBOOO17OOH1) LiBH 4 , THF-30 to -20 °C73%, + axial alcohol2) Ac 2 O, PyOH OMeO H O AcOMeO317OpNBOOHOOX = –CH(OCH 3 ) 2

Degradation of Ring AOH OHHO17 HOHOOHOHOOHOHMeO HOO AcOOHpTSAPhHHHOO AcOOHO 3 , CH 2 Cl 2-78 to -55°CMeOOpNBOOrefluxOpNB OOMeOthen Me 2 SOOOHHOO AcOOHAc 2 ONaOAcHOO AcOOHDBNPhH75°C17OO AcOOHOOpNBO100°C17AcOOpNBO50%(4 steps)OOOOOEnone Formation DetailsOH OH17HOHOHOOHOHB:OHOO AcOAcO17OOpNBOOHDBN, PhH-pNBOHB:OOHOOO AcO17OOOHHOOO-keteneOO AcOOH17OO AcOOHO17H +OOOOO

Synthesis of AnhydroryanodolOH OHHO HOHOOHHOOHOOOO AcOOHNaBH 4 , THFMeOH, 0°COO AcOOHOO! 90%HHOOOONaOH, THFOHHO HOH OHOOH3:1HOHHO HOHOOOHOOHHOOHHO HOCompletion of the SynthesisOOHNaOH, THF3:1HOHHO HOOHOOHOH OHHO HOHOOHHOOHOCF 3 CO 3 HNa 2 HPO 4 , DCEroom temp.85%OHOOHHO HOHOOOOHNaOH, THF3:2Li, NH 3THF! 60%HOOHHO HOOOHOOHOH OH OHHO HOHOOHHO(+)-ryanodol

Wood's Retrosynthetic Analysis of RyanodineRhodium-Mediated Claisen Rearrangement andPhenolic Oxidation / Singlet Oxygen Diels AlderOH OHHO HOHOORHOOHOOOOHOOOH OHRHOOROOOOOHOHPhenolic OxidationSinglet Oxygen Diels AlderOOHOOBnRhodium-MediatedClaisen RearrangementHOOCO 2 ROHN 2OBrBrGeneral StrategyOHOHWood's Phenolic Oxidation/Singlet Oxygen Diels AlderPhenolic [O]OOOO1 O 2OOOH OHHO HOHOOHHOOHModel System Substrate SynthesisOHO+!Cl(90% yield)OOAlCl 3 , !(45% yield)OOHHOOOH1. NaOH2. HCl(95% yield)EtOOOHH 2 , Pd(OH) 2OOBrOZn, !(52% yield)OEt3. NBS, DMF(70 %yield)EtOH(90% yield)Br

Wood's Phenolic Oxidation/Singlet Oxygen Diels Alder (cont.)Model System Validates the StrategyOH OHHO HOHOOHHOOHHOOOHPhI(O 2 CCF 3 ) 2MeCN(80% yield)OOO1 O 2(95% yield)OOOOOH 2 , Pd/CBrBrBr(95% yield)OOHOH OHOOOOHOOOHWood's Phenolic Oxidation/Singlet Oxygen Diels Alder (cont.)Strategy for the Real SystemOH OHHO HOHOOHHOOHHOOOHModelOOHOH OHHOOCO 2 HOHRealOOOHOH OHOOOOBrOBrOReal System Substrate SynthesisOOH1. NBS, DMF(70% yield)2. BnBr, K 2 CO 3(85% yield)OOBnBr1. (s-Bu)ONO,HCl (70% yield)2. NH 2 Cl, H 2 O/THF(78% yield)N 2OOBnBr

Wood's Phenolic Oxidation/Singlet Oxygen Diels Alder (cont.)Real System Validates the StrategyOH OHHO HOHOOHHOOHHO2 steps(80% yield)BnOOOEtLiCuMe 2(85% yield)BnOOOEtOOBnOOBnDIBAL-H(72% yield)L n RhRh 2 (OAc) 4!, PhH(62% yield)N 2+BnOOHBrBrOBnHOL n RhOOBnOBnOHOOBn[3,3]OHOOBnOHBrBrBrConcluding RemarksOOH OHHO HOHOOOHHONH– Lack of obvious disconnections– Many hydroxyls vs. compact polycyclic structure– Inclusion/installation of the pyrrole ester moiety– Synthesis of the C 6 –C 11 trans diol"...it can be concluded from this analysis that ryanodol is indeed a very complex diterpene..." – Deslongchamps