Product designation (1S,2S,3R,5S)-(+)-2,3-Pinanediol Pharma Grade API for Tablet / Capsule / Granule / Injection, Oral & Injectable corresponds to CAS 18680-27-8, molecular formula C₁₀H₁₈O₂, and relative molecular mass 170.25 g/mol. The substance is a chiral 2,3-diol derived from the pinane skeleton and is handled under pharmaceutical quality systems aligned with ICH Q7 for starting materials and advanced intermediates used in active pharmaceutical ingredient synthesis and formulation development. The (+) descriptor reflects the sign of specific optical rotation for the 1S,2S,3R,5S absolute configuration. In pharmaceutical development, the product is applied where stereochemical control of an intermediate or final active pharmaceutical ingredient is required, including solid oral dosage forms prepared by direct compression or granulation and injectable presentations employing aseptic filling or terminal sterilization. The material is not a monographed drug substance in the major pharmacopoeias; therefore, the release specification is product-specific and must be linked to the downstream critical quality attributes of the dosage form.

What Limits Chiral Purity Retention in Boronate Ester Synthesis?

The formation of cyclic boronate esters from (1S,2S,3R,5S)-(+)-2,3-pinanediol is a critical application in asymmetric synthesis. In a typical process configuration, the diol and an alkyl- or arylboronic acid are refluxed in toluene or cyclohexane in a jacketed reactor equipped with a Dean-Stark trap and pitched-blade turbine agitation. Water removal by azeotropic distillation drives the equilibrium toward the cyclic ester. Because residual water can hydrolyze the boronate and cause diastereomeric equilibration, the reaction headspace and solvent charge must be dried before charging. Process development studies generally recommend maintaining a nitrogen or argon overlay to limit oxidative degradation of the pinane skeleton. Extended exposure to strong oxidizers or to heat above the melting range can compromise chiral purity. Published data for this specific configuration is limited; therefore, water tolerance and hold-time studies should be performed on a lot-specific basis before setting a fixed drying limit. The stereochemical role of the diol is to generate a rigid boronate intermediate in which the approach of nucleophiles is biased by the pinane ring. Variation in the chiral purity of the starting diol directly affects the enantiomeric excess of downstream homologated intermediates. For this reason, chiral GC-FID using a cyclodextrin capillary column is more informative than achiral assay alone.

For immediate-release tablet and capsule development, the crystalline diol is typically screened in low-dose active blends because the material is more commonly used as a synthetic intermediate than as a high-dose final active ingredient. Blending with microcrystalline cellulose, mannitol, and croscarmellose sodium in a low-shear V-blender requires humidity control below 60% RH to limit agglomeration and surface adhesion. Particle size distribution is characterized by laser diffraction per USP 429; if segregation or content uniformity issues are observed in a low-dose blend, the material is pre-sieved through a 250 µm mesh or co-milled to reduce coarse particles. Tablet compression trials should evaluate punch sticking because low-melting chiral diols can soften under compacting pressure. For capsule filling, the powder may be dry-granulated by roller compaction when improved flow and bulk density are required.

Specification Framework and Analytical Release Criteria

Release testing for the pharma-grade material is organized around compendial methods adapted to a low-UV-absorbing crystalline diol. Because the compound lacks a strong chromophore, gas chromatography is preferred over HPLC-UV for assay and chiral purity. The following table lists representative acceptance criteria for a pharma-grade release specification; the valid certificate of analysis may impose tighter limits for a given lot.

Because the compound is a chiral intermediate rather than a final monographed drug substance, the specification must be linked to the synthetic route and the intended final dosage form. For injectable applications, endotoxin and particulate matter are additional release considerations. The nonsterile grade is not interchangeable with injectable-grade material unless endotoxin control and bioburden reduction are demonstrated through the full manufacturing and filtration train.

Granulation of the diol requires compatibility screening with aqueous binder systems because the material may be sensitive to prolonged moist heat. When a wet granulation step is used, hydroalcoholic granulation fluids are often selected over pure aqueous systems, and drying is performed in a vacuum tray dryer or fluid-bed dryer at reduced temperatures. The drying endpoint is confirmed by loss on drying rather than by fixed time alone. For roller compaction, the material is blended with microcrystalline cellulose and crospovidone before compaction; the ribbons are milled through a 1.0 mm screen to obtain granules suitable for tablet compression or capsule filling. Residual moisture after granulation should be brought below 0.5% w/w before lubrication with magnesium stearate, because free water can interact with the diol and alter blend flow.

When the Stereoisomer Is Used in Sterile Injectable Formulations

Sterile injectable presentations introduce a different control hierarchy. The diol is not inherently sterile, and dry-heat sterilization is generally avoided because the material may melt or soften before achieving a reliable sterilization temperature. If terminal sterilization of the finished dosage form is required, moisture heat exposure such as autoclaving at 121°C for 15 min must be supported by stereochemical stability data. Published data for this specific configuration is limited; therefore, forced degradation studies under ICH Q1A conditions should be used to establish that chiral purity remains within acceptance limits after moist-heat exposure. Aseptic filtration through a 0.22 µm PVDF or polyethersulfone membrane is common for solution dosage forms, but filter compatibility must be verified because low-molecular-weight diols can swell or plasticize certain membrane polymers. Particulate matter limits follow USP 788 for injectable products; subvisible particle counts and a bioburden-reduction step are required unless the process is fully aseptic. Endotoxin control is addressed through depyrogenation of containers, closures, and equipment, rather than through high-temperature treatment of the compound itself. The material should be stored at 2–8°C under inert gas and protected from moisture and oxidizing agents when injectable-grade status is to be maintained.

Compared with the enantiomeric (1R,2R,3S,5R)-(−)-2,3-pinanediol, the (1S,2S,3R,5S)-(+)-2,3-pinanediol produces opposite diastereofacial selection in chiral boronate reactions. This difference is not a minor quality attribute; it determines the absolute configuration of the downstream active pharmaceutical ingredient. The racemic 2,3-pinanediol mixture is unsuitable for stereoselective synthesis of a chiral API because it provides no enantiomeric induction and can generate a mixture of diastereomers. Compared with other chiral auxiliaries such as diisopropyl tartrate or camphor-derived diols, pinanediol-derived boronates often form crystalline intermediates with characteristic solubility and hydrolytic cleavage behavior. The pinane skeleton is comparatively rigid and can simplify isolation of the chiral intermediate by crystallization. However, complete removal of the chiral diol from the final API must be demonstrated where the diol is an auxiliary and not part of the drug substance structure. Residual chiral diol in the final API is controlled through purge factor calculations and routine release testing, typically by GC-FID or GC-MS. Technical-grade 2,3-pinanediol differs from the pharma-grade material in that it may contain higher levels of residual catalysts, uncontrolled stereoisomer content, and variable heavy metal profiles. Because those impurities can be carried into the final dosage form or synthetic intermediate, the pharma-grade product uses defined residual solvent and elemental impurity controls under ICH Q3C and ICH Q3D. The pharma-grade designation therefore reflects a quality management system and a release and stability testing program rather than a difference in chemical structure alone.

Operational boundaries are defined by moisture sensitivity, stereochemical stability, and the intended route of administration. The compound should not be blended with strong oxidizing agents, stored in open containers at elevated humidity, or processed under conditions that expose it to prolonged heat without supporting stability data. For oral dosage forms, the primary manufacturing risks are particle size control, moisture-induced agglomeration, and punch sticking during compression. For injectable dosage forms, the primary risks are endotoxin transfer, filter compatibility, and absence of terminal-sterilization stereochemical data. Where exact degradation pathways or process limits are not established, the filing must rely on lot-specific forced degradation data and process qualification rather than assumed stability. The material is therefore suitable for development and production only when the specification and processing controls are derived from the downstream product’s critical quality attributes and supported by compendial test methods.