C4 Butyric / Butanoic AcidShort-chain saturated fatty acid PostCustom 5′ • 3′ • selected internal + Available routesPost-synthetic conjugation is the primary flexible route. Custom modifier or support development can be reviewed where needed. Architecture noteUseful for short-chain comparisons and specialty conjugates where minimal hydrophobic contribution is desired.
C6 Caproic / Hexanoic AcidShort-chain saturated fatty acid PostCustom 5′ • 3′ • selected internal + Available routesPost-conjugation or custom direct chemistry depending on desired linker and placement. Architecture noteShort-chain option for systematic C4-C22 SAR and linker-versus-lipid comparisons.
C8 Caprylic / Octanoic AcidMedium-chain saturated fatty acid PostCustom 5′ • 3′ • selected internal + Available routesPost-synthetic conjugation is generally straightforward; custom amidite or support routes can be evaluated. Architecture noteProvides a medium-chain comparison point with moderate hydrophobic character.
C10 Capric / Decanoic AcidMedium-chain saturated fatty acid PostCustom 5′ • 3′ • selected internal + Available routesPost-conjugation is the broadest route; specialty direct chemistry can be considered for defined architecture programs. Architecture noteIntermediate chain-length option for systematic hydrophobicity studies.
C12 Lauric / Dodecanoic AcidLonger-chain saturated fatty acidMultiple Incorporation Routes Amidite3′ SupportPost 5′ • 3′ • internal + Direct modifier chemistryDodecanamido-type phosphoramidite can support appropriate 5′ or internal incorporation. 3′ supportSelected C12 support chemistry can provide defined 3′ lipid placement. Post-conjugation5′, 3′ or selected internal handles can be used when a different linkage or spacer is desired. Architecture noteDirect and conjugation routes may create different linkages even though both are described as C12-modified oligos.
C14 Myristic / Tetradecanoic AcidLong-chain saturated fatty acid PostCustom 5′ • 3′ • internal + Available routesPost-synthetic conjugation is highly flexible; specialty direct chemistry can be developed for defined architecture programs. Architecture noteUseful for mono-, di-, and multivalent lipid-siRNA comparisons.
C16 Palmitic / Hexadecanoic AcidLong-chain saturated fatty acidMultiple Incorporation Routes Amidite3′ SupportPost2′-O 5′ • 3′ • internal • nucleotide-specific + Direct modifier chemistryPalmitamido-C6/C7-type phosphoramidites can provide defined terminal or internal C16 modifier architectures depending on reagent design. 3′ supportC16-functionalized solid support provides a defined 3′ lipid architecture. 2′-O nucleoside library2′-O-C16-A, -C, -G and -U provide site-specific lipidated nucleotide placement. Post-conjugation5′, 3′, selected internal, branched, dual- and multivalent C16 architectures can be evaluated using suitable handles and linkers. Important: a post-conjugated palmitic-acid oligo, a Palmitamido-C7 modifier, and a 2′-O-C16 nucleotide are structurally different products and should be specified separately.
C18 Stearic / Octadecanoic AcidLong-chain saturated fatty acidMultiple Incorporation Routes Amidite3′ SupportPost 5′ • 3′ • internal + Direct modifier chemistryStearamido or stearyl-type phosphoramidites can support defined direct incorporation. 3′ supportSelected C18 supports provide 3′ lipid incorporation. Post-conjugationFlexible route for 5′, 3′, selected internal and multivalent C18 architectures. Architecture noteHigh hydrophobicity makes purification, solubility, and final formulation especially important.
C20 Arachidic / Eicosanoic AcidLong-chain saturated fatty acid PostCustom 5′ • 3′ • internal + Available routesPost-synthetic conjugation is typically the most flexible route; specialty amidite/support development is project specific. Architecture noteLong-chain hydrophobic architecture requiring careful handling, purification and formulation planning.
C22 Behenic / Docosanoic AcidVery-long-chain saturated fatty acidMultiple Incorporation Routes 3′ SupportPost2′-OCustom 5′ • 3′ • internal • nucleotide-specific + 3′ supportDocosanamido-type solid support provides a defined 3′ C22 architecture. 2′-O nucleoside library2′-O-C22-A, -C, -G and -U provide site-specific nucleotide placement. Post-conjugation5′, 3′, selected internal, and multivalent C22 architectures can be built using suitable handles and linkers. Architecture noteA terminal C22 fatty-acid conjugate and a 2′-O-C22 modified nucleotide are distinct molecular architectures.